The occurrence of p53, bcl-2 and heat shock protein (HSP) expression in ovarian tumours was examined and the correlation was investigated between the expression of these proteins and other disease parameters, including FIGO stage, histological subtype, tumour differentiation and steroid hormone receptor status. We analysed p53, bcl-2 and HSP expression in 100 smears of patients with epithelial ovarian carcinomas, 16 smears of patients with borderline malignancy and 20 smears of patients with benign ovarian neoplasms by using immunocytochemical techniques. There were 29 patients with stage I disease, 24 with stage II disease, 40 with stage III disease and seven with stage IV disease according to the FIGO classification. The sensitivities and specificities of bcl-2, p53 and HSP for malignancy were 53% and 40%, 43% and 80%, and 37% and 90%, respectively. HSP was statistically significantly associated with malignant rather than benign tumours. Significant association was also observed between bcl-2 and p53, and p53 and HSP. The association of HSP with malignant tumours is confined to the premenopausal group of patients and in this group by itself there is also a significant association between p53 and malignancy. HSP and p53 were associated with undifferentiated carcinomas, bcl-2 and p53 expression is reduced as disease stage progresses in serous carcinomas and bcl-2 expression is increased as disease progresses in endometrioid carcinomas. There was no significant association between bcl-2 and ER/PR status. In conclusion, HSP has a high specificity for malignant ovarian tumours, bcl-2 and p53 have only moderate to low sensitivity and specificity. Changes in the frequency of bcl-2 and p53 overexpression between FIGO I and FIGO III stage disease of different ovarian carcinomas indicate a different role of these substances in cellular survival mechanisms in different carcinomas. bcl-2 probably is associated with cell proliferation but not with differentiation.