A study of 130 biopsies from cases of histologically confirmed normal cervix (30), cervicitis (28), cervical intraepithelial neoplasia (CINI-CIN III, 29), and cervical cancer (43) was performed to determine the presence of human papillomavirus (HPV) type 16 DNA sequences. The polymerase chain reaction technique was adopted using two oligonucleotides as primer pairs in the HPV16 early 6 (E6) gene open reading frame (ORF). The rates of HPV16 infection in normal tissues, cervicitis, CINI-CIN III and cervical cancer were found to be 16.67% (5/30), 25.00% (7/28), 41.38% (12/29) and 69.77% (30/43), respectively. Statistical analysis showed that the relative risk (RR) of association between HPV16 infection and the development of cervicitis, CINs and cervical carcinomas was increased with the severity of cervical lesions, from 1.0 (normal) to 1.67, 4.62 (P < 0.05; 95% CI 0.28-8.95) and 11.54 (P < 0.001; 95% CI 3.94-33.81), respectively. Our results strongly support the idea that the development of cervical precancerous lesions and cervical carcinomas is closely associated with HPV16 infection.