Sequences of HIV-1 pol gene were determined by direct sequencing from a Japanese patient with primary HIV-1 infection. The patient did not receive antiretroviral therapies. However we observed a HIV-1 mutant strain associated with zidovudine (ZDV) resistance. The patient had both the codon 70 and the codon 215 amino acid substitutions in the RT region. Our data indicated that the patient was infected with a HIV-1 mutant strain associated with ZDV resistance and this is the first report in Japan.