The expression of bcl-2 protein was analysed immunohistochemically in 202 female breast carcinomas. The intensity of bcl-2 expression was inversely related to tumour grade (P < 0.0001), tumor necrosis (P < 0.0001), mitotic index (P < 0.0001), oestrogen receptor content (P < 0.0001), progesterone receptor content (P = 0.0007), S-phase fraction (P = 0.00047), and apoptotic index (P = 0.087). A high fraction of bcl-2-positive cells was related to ductal or lobular type (P = 0.03) and slight nuclear pleomorphism (P = 0.03). Heterogeneous expression of bcl-2 protein was associated with high grade (P = 0.02), severe nuclear pleomorphism (P = 0.02), DNA aneuploidy (P = 0.018), high S-phase fraction (P = 0.05), and early metastasis (P = 0.03). Intense expression of bcl-2 protein was significantly related to favourable outcome in the entire cohort (P = 0.0013), as well as in axillary lymph node-negative (ANN) tumours (P = 0.0124). Long recurrence-free periods in the entire cohort (P = 0.037) and in ANN tumours (P = 0.08) were confined to cases with intense expression of bcl-2 protein. In multivariate analysis, bcl-2 expression had no independent prognostic value in the entire cohort or in axillary lymph node-negative breast carcinomas, whereas it was a weak independent prognostic factor in axillary lymph node-positive breast carcinomas.