Objective - To assess the prevalence of sexually transmitted pathogens in drug-addicted women in Tel Aviv, Israel. Design - A prospective study conducted between March and July 1987. Setting - A methadone clinic in Tel Aviv, Israel. Subjects - Sixty four asymptomatic female drug addicts were studied; 38 of them were declared practising prostitutes. Methods - Cervical specimens were obtained for cultures, and blood samples were drawn for serological tests. Demographic data and sexual histories were obtained using a standard questionnaire. Results - Chlamydia trachomatis was detected in the cervix of 25% of women; 98% had antibody titres (> 1:64). Mycoplasma hominis and Ureaplasma urealyticum were isolated in 57% and 65% respectively. Gardnerella vaginalis was detected in 17% of women, and herpes simplex virus was cultured from two prostitutes. Five per cent of women were carriers of HB(s)Ag, while 57% had HB(s) and/or HB(c) antibodies. Only one prostitute had specific treponemal antibodies. In no case were gonococci or groupo B streptococci isolated, and HIV serology was invariably negative. Conclusion - Chlamydia and genital mycoplasmas appear to be the prevailing pathogens in Israeli drug-addicted women, while gonococci and Treponema pallidum occur only rarely.