With the aim of evaluating the correlation between dysplastic lesions of the uterine cervix associated or not with condylomatosis and Chlamydia T. infection, we carried out a serological study of anti-Chlamydia species-specific antibodies and a direct and/or a cultural investigation on a sample of 320 women who performed a Pap-test. The serological examination showed positivity (titer greater than or equal to 1:32) in 49 control subjects (with negative cytology) (23.7%); in 27 cases (43.5%) with actual diagnosis of condylomatosis/CIN associated or not with condylomatosis and in 28 cases (54.9%) with previous diagnosis of condylomatosis/CIN associated or not with condylomatosis. The cultural investigation did not show any significant difference among the groups above mentioned. Finally, the frequency of positive cases for anti-Chlamydia antibodies was estimated for each grade of actual or previous CIN: a greater frequency of positivity was noted in cases with CIN 3 (75%).