275 adolescents aged 10-19 receiving attention at the infantojuvenile department of pregnancy interruption and of sexually transmitted infections of "Ramón Gonzalez Coro" and "Eusebio Hernández" Gynecoobstetric Teaching Hospitals, both in Havana City, were studied from August, 1999, to September, 2000, aimed at knowing the behavior of the infection caused by Trichomonas vaginalis in this population group. The results yielded 18.1 % of positivity to parasitosis. It was proved by the calculation of relative risk that the adolescents that had an active or past infection due to Trichomonas vaginalis have more possibilities of getting an infection produced by human Papilomavirus than those without this condition. It was demonstrated that 78 (28.3 %) of the total of patients examined had some type of lesion in the uterine cervix. Some risk factors as non using condon, having multiple sexual partners and the early beginning of sexual relations, which may facilitate the adquisition of this parasitosis in a population so vulnerable as the adolescents, were made known.