diff --git a/usr.bin/mt/mt.1 b/usr.bin/mt/mt.1
index b9340da1b133..b48a85380679 100644
--- a/usr.bin/mt/mt.1
+++ b/usr.bin/mt/mt.1
@@ -266,6 +266,9 @@ Value  Width        Tracks    Density         Code Type Reference   Note
 0x16   12.7  (0.5)   48        394  (10,000)  MFM   C   X3.193-1990  1
 0x17   12.7  (0.5)   48      1,673  (42,500)  MFM   C   X3B5/91-174  1
 0x18   12.7  (0.5)  112      1,673  (42,500)  MFM   C   X3B5/92-50   1
+0x19   12.7  (0.5)  128      2,460  (62,500)  RLL   C   DLTapeIII    6,7
+0x1A   12.7  (0.5)  128      3,214  (81,633)  RLL   C   DLTapeIV(20) 6,7
+0x1B   12.7  (0.5)  208      3,383  (85,937)  RLL   C   DLTapeIV(35) 6,7
 0x1C    6.3  (0.25)  34      1,654  (42,000)  MFM   C   QIC-385M     1,6
 0x1D    6.3  (0.25)  32      1,512  (38,400)  GCR   C   QIC-410M     1,6
 0x1E    6.3  (0.25)  30      1,385  (36,000)  GCR   C   QIC-1000C    1,6
@@ -282,6 +285,7 @@ Value  Width        Tracks    Density         Code Type Reference   Note
 0x29   12.7  (0.5)
 0x2A
 0x2B   12.7  (0.5)    3          ?        ?     ?   C   X3.267       5
+0x41   12.7  (0.5)  208      3,868  (98,250)  RLL   C   DLTapeIV(40) 6,7
 .Ed
 .Bd -literal -offset 3n
 Code Description                                   Type Description
@@ -302,6 +306,8 @@ NOTES
 5. Helical scan.
 6. This is not an American National Standard.  The reference is based on
    an industry standard definition of the media format.
+7. DLT recording: serially recorded track pairs (DLTapeIII and
+   DLTapeIV(20)), or track quads (DLTapeIV(35) and DLTapeIV(40)).
 .Ed
 .Sh ENVIRONMENT
 If the following environment variable exists, it is utilized by
diff --git a/usr.bin/mt/mt.c b/usr.bin/mt/mt.c
index 24b25d9d461c..df2cc6be5268 100644
--- a/usr.bin/mt/mt.c
+++ b/usr.bin/mt/mt.c
@@ -438,6 +438,9 @@ struct densities {
 	{ 0x16,	394,	10000,	"X3.193-1990" },
 	{ 0x17,	1673,	42500,	"X3B5/91-174" },
 	{ 0x18,	1673,	42500,	"X3B5/92-50" },
+	{ 0x19, 2460,   62500,  "DLTapeIII" },
+	{ 0x1A, 3214,   81633,  "DLTapeIV(20GB)" },
+	{ 0x1B, 3383,   85937,  "DLTapeIV(35GB)" },
 	{ 0x1C, 1654,	42000,	"QIC-385M" },
 	{ 0x1D,	1512,	38400,	"QIC-410M" },
 	{ 0x1E, 1385,	36000,	"QIC-1000C" },
@@ -451,6 +454,7 @@ struct densities {
 	{ 0x26,	3816,	97000,	"DDS-4" },
 	{ 0x27,	3056,	77611,	"Mammoth" },
 	{ 0x28,	1491,	37871,	"X3.224" },
+	{ 0x41, 3868,   98250,  "DLTapeIV(40GB)" },
 	{ 0, 0, 0, NULL }
 };