The complete nucleotide sequence of both the 5' and 3' long terminal repeats (LTR's) has been determined for a human endogenous retroviral genome. These sequences are 593 and 590 nucleotides long and have diverged from one another by 8.8 percent. The LTR's resemble those of functional mammalian type C retroviruses in length and in the presence and location of eukaryotic promoter sequences. The 5' LTR is followed by a presumptive primer binding site unlike that of any known mammalian type C retrovirus, exhibiting 17 out of 18 nucleotides complementary to arginine transfer RNA rather than proline transfer RNA.