diff --git a/src/iperf.h b/src/iperf.h
index 188f06a..22037df 100644
--- a/src/iperf.h
+++ b/src/iperf.h
@@ -174,6 +174,9 @@ struct iperf_test
     char     *congestion;			/* -C option */
     char     *pidfile;				/* -P option */
 
+    char     *logfile;				/* --logfile option */
+    FILE     *outfile;
+
     int       ctrl_sck;
     int       listener;
     int       prot_listener;
diff --git a/src/iperf3.1 b/src/iperf3.1
index d2d13ba..588ef3b 100644
--- a/src/iperf3.1
+++ b/src/iperf3.1
@@ -55,6 +55,9 @@ give more detailed output
 .BR -J ", " --json " "
 output in JSON format
 .TP
+.BR --logfile " \fIfile\fR"
+send output to a log file.
+.TP
 .BR -d ", " --debug " "
 emit debugging output.
 Primarily (perhaps exclusively) of use to developers.
diff --git a/src/iperf_api.c b/src/iperf_api.c
index 05de7b7..744e74c 100644
--- a/src/iperf_api.c
+++ b/src/iperf_api.c
@@ -562,6 +562,7 @@ iperf_parse_arguments(struct iperf_test *test, int argc, char **argv)
         {"sctp", no_argument, NULL, OPT_SCTP},
 #endif
 	{"pidfile", required_argument, NULL, 'I'},
+	{"logfile", required_argument, NULL, OPT_LOGFILE},
         {"debug", no_argument, NULL, 'd'},
         {"help", no_argument, NULL, 'h'},
         {NULL, 0, NULL, 0}
@@ -791,6 +792,9 @@ iperf_parse_arguments(struct iperf_test *test, int argc, char **argv)
 		test->pidfile = strdup(optarg);
 		server_flag = 1;
 	        break;
+	    case OPT_LOGFILE:
+		test->logfile = strdup(optarg);
+		break;
             case 'h':
             default:
                 usage_long();
@@ -798,6 +802,18 @@ iperf_parse_arguments(struct iperf_test *test, int argc, char **argv)
         }
     }
 
+    /* Set logging to a file if specified, otherwise stdout*/
+    if (test->logfile) {
+	test->outfile = fopen(test->logfile, "a+");
+	if (test->outfile == NULL) {
+	    i_errno = IELOGFILE;
+	    return -1;
+	}
+    }
+    else {
+	test->outfile = stdout;
+    }
+
     /* Check flag / role compatibility. */
     if (test->role == 'c' && server_flag) {
 	i_errno = IESERVERONLY;
@@ -2524,9 +2540,8 @@ iperf_json_finish(struct iperf_test *test)
     str = cJSON_Print(test->json_top);
     if (str == NULL)
         return -1;
-    fputs(str, stdout);
-    putchar('\n');
-    fflush(stdout);
+    fprintf(test->outfile, "%s\n", str);
+    iflush(test);
     free(str);
     cJSON_Delete(test->json_top);
     test->json_top = test->json_start = test->json_intervals = test->json_end = NULL;
@@ -2608,9 +2623,15 @@ iprintf(struct iperf_test *test, const char* format, ...)
     int r;
 
     if (test->title)
-        printf("%s:  ", test->title);
+        fprintf(test->outfile, "%s:  ", test->title);
     va_start(argp, format);
-    r = vprintf(format, argp);
+    r = vfprintf(test->outfile, format, argp);
     va_end(argp);
     return r;
 }
+
+int
+iflush(struct iperf_test *test)
+{
+    return fflush(test->outfile);
+}
diff --git a/src/iperf_api.h b/src/iperf_api.h
index e04b20f..9840fa0 100644
--- a/src/iperf_api.h
+++ b/src/iperf_api.h
@@ -27,6 +27,7 @@ struct iperf_stream;
 
 /* short option equivalents, used to support options that only have long form */
 #define OPT_SCTP 1
+#define OPT_LOGFILE 2
 
 /* states */
 #define TEST_START 1
@@ -225,7 +226,7 @@ int iperf_clearaffinity(struct iperf_test *);
 
 /* Custom printf routine. */
 int iprintf(struct iperf_test *test, const char *format, ...) __attribute__ ((format(printf,2,3)));
-
+int iflush(struct iperf_test *test);
 
 /* Error routines. */
 void iperf_err(struct iperf_test *test, const char *format, ...) __attribute__ ((format(printf,2,3)));
@@ -251,6 +252,7 @@ enum {
     IEFILE = 14,            // -F file couldn't be opened
     IEBURST = 15,           // Invalid burst count. Maximum value = %dMAX_BURST
     IEENDCONDITIONS = 16,   // Only one test end condition (-t, -n, -k) may be specified
+    IELOGFILE = 17,	    // Can't open log file
     /* Test errors */
     IENEWTEST = 100,        // Unable to create a new test (check perror)
     IEINITTEST = 101,       // Test initialization failed (check perror)
diff --git a/src/iperf_client_api.c b/src/iperf_client_api.c
index 0e0f1ad..16fe942 100644
--- a/src/iperf_client_api.c
+++ b/src/iperf_client_api.c
@@ -356,7 +356,7 @@ iperf_run_client(struct iperf_test * test)
 	iprintf(test, "%s\n", version);
 	iprintf(test, "%s", "");
 	fflush(stdout);
-	printf("%s\n", get_system_info());
+	iprintf("%s\n", get_system_info());
     }
 
     /* Start the client and connect to the server */
@@ -479,5 +479,7 @@ iperf_run_client(struct iperf_test * test)
 	iprintf(test, "%s", report_done);
     }
 
+    iflush(test);
+
     return 0;
 }
diff --git a/src/iperf_error.c b/src/iperf_error.c
index d4cb444..51b0f8b 100644
--- a/src/iperf_error.c
+++ b/src/iperf_error.c
@@ -28,11 +28,16 @@ iperf_err(struct iperf_test *test, const char *format, ...)
     if (test != NULL && test->json_output && test->json_top != NULL)
 	cJSON_AddStringToObject(test->json_top, "error", str);
     else
-	fprintf(stderr, "iperf3: %s\n", str);
+	if (test && test->outfile) {
+	    fprintf(test->outfile, "iperf3: %s\n", str);
+	}
+	else {
+	    fprintf(stderr, "iperf3: %s\n", str);
+	}
     va_end(argp);
 }
 
-/* Do a printf to stderr, then exit. */
+/* Do a printf to stderr or log file as appropriate, then exit. */
 void
 iperf_errexit(struct iperf_test *test, const char *format, ...)
 {
@@ -45,7 +50,12 @@ iperf_errexit(struct iperf_test *test, const char *format, ...)
 	cJSON_AddStringToObject(test->json_top, "error", str);
 	iperf_json_finish(test);
     } else
-	fprintf(stderr, "iperf3: %s\n", str);
+	if (test && test->outfile) {
+	    fprintf(test->outfile, "iperf3: %s\n", str);
+	}
+	else {
+	    fprintf(stderr, "iperf3: %s\n", str);
+	}
     va_end(argp);
     iperf_delete_pidfile(test);
     exit(1);
@@ -116,6 +126,10 @@ iperf_strerror(int i_errno)
         case IEENDCONDITIONS:
             snprintf(errstr, len, "only one test end condition (-t, -n, -k) may be specified");
             break;
+	case IELOGFILE:
+	    snprintf(errstr, len, "unable to open log file");
+	    perr = 1;
+	    break;
         case IENEWTEST:
             snprintf(errstr, len, "unable to create a new test");
             perr = 1;
diff --git a/src/iperf_server_api.c b/src/iperf_server_api.c
index b21e042..76290ea 100644
--- a/src/iperf_server_api.c
+++ b/src/iperf_server_api.c
@@ -65,8 +65,8 @@ iperf_server_listen(struct iperf_test *test)
     }
 
     if (!test->json_output) {
-	printf("-----------------------------------------------------------\n");
-	printf("Server listening on %d\n", test->server_port);
+	iprintf(test, "-----------------------------------------------------------\n");
+	iprintf(test, "Server listening on %d\n", test->server_port);
     }
 
     // This needs to be changed to reflect if client has different window size
@@ -450,7 +450,7 @@ iperf_run_server(struct iperf_test *test)
 	iprintf(test, "%s\n", version);
 	iprintf(test, "%s", "");
 	fflush(stdout);
-	printf("%s\n", get_system_info());
+	iprintf(test, "%s\n", get_system_info());
     }
 
     // Open socket and listen
@@ -602,6 +602,8 @@ iperf_run_server(struct iperf_test *test)
 	    return -1;
     } 
 
+    iflush(test);
+
     if (test->server_affinity != -1) 
 	if (iperf_clearaffinity(test) != 0)
 	    return -1;
diff --git a/src/locale.c b/src/locale.c
index 6fa4ade..cb58922 100644
--- a/src/locale.c
+++ b/src/locale.c
@@ -78,6 +78,7 @@ const char usage_longstr[] = "Usage: iperf [-s|-c host] [options]\n"
 #endif
                            "  -V, --verbose             more detailed output\n"
                            "  -J, --json                output in JSON format\n"
+                           "  --logfile f               send output to a log file\n"
                            "  -d, --debug               emit debugging output\n"
                            "  -v, --version             show version information and quit\n"
                            "  -h, --help                show this message and quit\n"