Expression of the epidermal growth factor-receptor (EGF-R) and the proliferating cell nuclear antigen (PCNA) was immunohistochemically studied in 75 ovarian cancer samples using formalin-fixed, parafin-embedded tissue. Correlations between these factors and conventional histomorphologic factors were investigated. 44 (58.7%) tumors were EGF-R positive (> 10% positive cells). 18 tumors (24%) showed a weak EGF-R-expression (< or = 50% positivity) and 26 tumors (34.7%) had a strong EGF-R-expression. Expression of EGF-R did not correlate with any of the other prognostic factors investigated. The PCNA-proliferative fraction was classified using the median value (< or = 34%/ > 34%) and a categorization in three groups (< 20%/20%-50%/ > 50%). PCNA-expression showed no correlation with FIGO-stage, histologic tumor type, lymph node-status and EGF-R. However, both PCNA-classifications correlated with the size of the residual tumor (PCNA < or = 34%/ > 34%/p = 0.046; PCNA < 20%/20%-50%/ > 50%/p = 0.086) and the histologic grading (p = 0.076; p = 0.02 respectively). Thus, the PCNA-proliferative fraction might be an additional indicator for tumor aggressiveness and disease outcome.