A total of 101 primary cervical adenocarcinomas were analyzed for the presence of p16INK4a and MIB-1 expression in correlation with the presence of 'high-risk' types of human papillomavirus (HR-HPV) and clinical outcome. We found that adenocarcinoma grading showed a significant negative correlation to p16INK4a levels (p=0.001): i.e. we found less intense p16 staining in poorly differentiated tumors than in more highly differentiated tumors as well as a highly significant correlation between HPV infection and higher levels of p16INK4a staining (p=0.00), which was similar for different HPV-types. Tumor suppressor protein p16INK4a levels were higher in HPV positive than in HPV negative tumors. Higher levels of the proliferation marker MIB-1 were associated with poorer outcome. Higher MIB-1 levels were seen in tumors with a lower grade and higher stage at diagnosis. Moreover, MIB-1 levels seem to be higher in tumors due to infection with HPV 16 and 18 compared with HPV 45. MIB-1 may be a helpful marker in grading adenocarcinoma: a high level of expression of MIB-1 indicates a low grade of tumor, whereas high expression of p16INK4a indicates a highly differentiated of the tumor. Thus, immunostaining for p16INK4a appears to be a useful diagnostic tool for cervical adenocarcinoma.