HIV-1 genome regions encoding the gp120 V3 part were sequenced in samples isolated from persons belonging to the category of those infected in the Rostov-Elista outbreak and having the common infection source. Samples were obtained from 5 patients in 1992 and in 2001. A total of 27 sequences obtained in 1992 and 35 sequences obtained in 2001, 2 to 8 sequences for each patient, were analyzed. The diversity level of V3 sequences made, in some patients, 2.2% in 1992 and went up to 4.2% in 2001 samples (p < 0.07). The ratio between the synonymous and non-synonymous substitutions was determined for the gp120 V3 region. The mean ratio value made 0.12 in 1992 samples and 0.23 in 2001 samples. The obtained data confirm the assumption, made previously in a population analysis, on the evolution of the gp120 V3 epitope towards substitution of the Lg initial structure in positions 14 and 15 (through intermediate stages represented by the IG and FG structures) for the FA structure.