In order to evaluate the influence of pregnancy on the presence of human papillomavirus (HPV) in the lower female genital tract, cervical smears of 92 pregnant and 96 non-pregnant women, matched by age, were examined for the presence of HPV-DNA by means of Southern blot hybridization. All patients had negative PAP smears. Twenty-six (28%) of the pregnant women and 12 (12.5%) of the non-pregnant women were positive for HPV. HPV 16 accounted for 42% of all positive pregnant cases and only 25% of the positive non-pregnant cases. Smears of pregnant patients contained more than 10 pg viral DNA in 45% of the cases against 20% in the non-pregnant group. HPV 16 showed the most active replication in both groups. This study demonstrates an increased prevalence of HPV (preferentially of HPV 16) and a higher replication rate of viral DNA during pregnancy.