The PCR was employed to detect and characterize the bovine immunodeficiency-like virus (BIV), which is a newly recognized member of the I entivirinae of the retroviruses. Degenerate primers representing the conserved regions in the pol genes of the Lentivirinae, were used to detect proviral DNA obtained from the bovine embryonic spleen cell cultures infected with BIV. The PCR amplified DNA fragment was molecularly cloned and sequenced. The BIV DNA fragment contained a sequence identical to that reported by Garvey et al. (Garvey et al., 1990. Virology, 175, 391-409). With the degenerate primers, peripheral blood mononuclear cells (PBMCs) of sick cattle and cells cultured with BIV were tested to determine genetic variation of BIV pol conserved sequence. We found the sequence heterogeneity within cultures and most variations occurred at the third base of codons that would not lead to amino acid substitutions. Another change was GAG (Glu) to AAG (Lys) within the BIV isolates. Interestingly, the altered sequence is also found in other lentiviruses such as HIV-2, SIV mac, CAEV and EIAV.