Human papillomavirus (HPV) has been implicated in the development of cervical intraepithelial neoplasia (CIN). To test the hypothesis that the known relationship between HPV and CIN might be modified by the altered immune status of pregnancy the cytologic, colposcopic and histologic findings in 176 pregnant and 515 nonpregnant patients referred to a colposcopy clinic were prospectively compared. No difference between the two groups was found regarding the frequency with which CIN and HPV were detected cytologically, colposcopically and histologically. Confidence intervals for the probability of CIN in the presence of HPV for the two groups were calculated. At the 80% confidence interval the two groups were reassuringly similar. Pregnancy did not alter the relationship of CIN to HPV. Despite the relatively small size of our study population, it is unlikely that a larger study would demonstrate a difference. Interestingly a 3% cervical carriage rate of HPV in pregnancy was demonstrated. What, if any, effect this has upon the unborn child is unknown at this time.