Cyclin Dl, one of Gl cyclin gene subfamily, and human papillomaviruses (HPV) oncoprotein E7 have a homology in binding sites for the retinoblastoma tumor-suppressor protein. In order to evaluate the role of cyclin Dl in human cervical carcinogenesis, the level of its expression was measured and compared to HPV infection. In these studies, 38 normal control cases, 22 carcinoma in situ (CIN) cases, and 16 invasive cervical carcinomas were analyzed by immunocytochemistry and polymerase chain reactions for the detection of expression of cyclin Dl and infection of HPV type 16 and 18, respectively. The cyclin Dl expression was significantly lower in CIN and invasive carcinoma than normal control group regardless of HPV infection (p=0.026). The decreased expression of cyclin Dl in normal control group was not related with HPV infection. However, the levels of expression of cyclin Dl in CIN and invasive carcinoma were correlated with HPV 16and 18 (p 0.026). The expression of cyclin E was not changed in HPV 16 and 18 infected cases. These data provide the evidence that cyclin Dl expression in the lesions of cervical tumor is decreased and it is related with HPU infection.