Community based survey on a sample of commercial sex workers in one red light area of Calcutta, was carried out to determine prevalence of sexually transmitted diseases (STD) including HIV infection and related risk factors. An alarmingly high prevalence of STDs (80.56 per cent) but low HIV-seropositivity (1.13 per cent) was observed. Candida albicans, Neisseria gonorrhoeae and Trichomonas vaginalis were detected in 23.24, 13.24 and 11.11 per cent of genital specimens respectively. BY TPHA test 62.97 per cent of the sera were reactive for Treponema pallidum. Duration in the profession of sex workers was found to have an association with seropositivity for syphilis. Prevalence of HIV infection might be low at present, but conditions were highly favourable for rapid spread of infection.