The molecular characterization of HIV-1 isolates in drug-naive cases in the early stages of HIV disease was studied in 128 cases from Mumbai (Bombay), India. Subtype C was largely predominant followed by A-C intersubtype recombinants, one subtype A and one CRF01 AE. Compared to subtype B, subtype C exhibited an important polymorphism; the percentages of substitutions could reach more than 90%. Two isolates showed M184V substitution the reverse transcriptase indicating resistance to 3TC.