OBJECTIVE—To establish the prevalence of sexually transmitted organisms and other genital organisms in potentially sexually abused children. DESIGN—Prospective study of children attending an inner London department of community paediatrics for evaluation of possible sexual abuse. SUBJECTS—Children under 16 referred for evaluation of possible sexual abuse. OUTCOME MEASURES—Prevalence of sexually transmitted organisms in relation to age, symptoms, and type of abuse. RESULTS—Swabs were taken from 159 of 242 girls evaluated. The overall prevalence of sexually transmitted organisms was 3.7%: three girls were infected with gonorrhoea, four with Trichomonas vaginalis, and two with Chlamydia trachomatis. One girl had all three infections plus mycoplasmas. Mycoplasmas were identified in 22% of girls swabbed. Of 30 boys swabbed, none yielded a sexually transmitted organism. CONCLUSIONS—There is a low prevalence of definitely sexually transmitted organisms in children who might have been abused. Other organisms possibly associated with sexual activity can be identified in this population. Screening for infection should be mandatory in presumed sexually abused girls with vaginal discharge and ideally should be undertaken in all children attending for evaluation of sexual abuse.