Polymorphisms in CCR2 and CCR5 genes reportedly affect HIV-1 transmission and disease progression in HIV-1-infected individuals. In the study presented here, we examined the effects of CCR2 and CCR5 polymorphisms on HIV-1 transmission in 74 Thai females who were exposed to HIV but seronegative (ESN) and in 347 HIV-seropositive females. We found that the combination of 2 non-synonymous substitutions, CCR2 V64I and CCR5 G316A, tended to occur more frequently in ESN females (2 of 74) than in HIV-1 infected females (1 of 347) (P = 0.08). This suggested that non-synonymous substitution in the CCR5 gene also affects HIV-1 transmission in an Asian population in which the CCR5-Delta32 is very rare.