BACKGROUND: Adolescence in the age bracket with the highest incidence of sexually transmitted diseases (STDs). An observational study was performed in symptomatic patients attending our Outpatient Clinic for STDs in order to evaluate the diffusion of genital infections in the adolescent population and the different epidemiological distribution compared to adults. METHODS: The incidence of these infections was compared in two groups of patients attending the clinic between April 1995 and April 1999. The first consisted of 54 teenagers (13-19 years-old) and the second, used as a control, consisted of 917 women of child-bearing age (20-40 years). All patients underwent clinical examinations and microbiological tests of vaginal secretions (bacterioscopic test on coloured plates using the Gram method, cold tests, cultural assay of bacteria and fungi, assay for (Chlamydia trachomatis, Mycoplasma spp., Neisseria gonorrhoeae, Herpes simplex virus). RESULTS: The most common genital infection in teenagers was candidosis (35% vs 23.9%), followed by bacterial vaginosis (31.9% vs 25.8%) and mixed flora vaginitis (25.9% vs 22.6%). HSV was found in 1.8% of adolescents (vs 0.6%), in selected cases, Chlamydia and Mycoplasma were present in 16.6% (vs 1.1%) and 50% (vs 28%) of teenagers respectively. CONCLUSIONS: All genital infections were more frequent in the study population of adolescents compared to the control group. The adolescent population should be the target of a serious and systematic programme of prevention in order to ward off the sequelae of early and often irresponsible sexual activity.