The human beclin-1 gene, located on chromosome 17q21, has been identified as the mammalian orthologue of Atg6 (autophagy-related gene) and may be a haploinsufficient tumor suppressor gene. The function and expression of beclin-1 in human breast cancer are largely unknown. We investigated the expression of beclin-1 and bcl-2 in human breast cancer. Tissue samples from 125 cases of invasive breast cancer were used for the present study. Immunohistochemical staining for beclin-1 and bcl-2 was evaluated using tissue microarray, then the 2 proteins were correlated with clinicopathologic parameters. Positive beclin-1 expression and bcl-2 expression in breast cancer tissue were observed in 53 cases (42.4%) and 48 cases (38.4%), respectively. Beclin-1 expression was inversely correlated with bcl-2 expression in breast cancer tissue (P = .035). Beclin-1 expression significantly correlated with nuclear pleomorphism and mitotic count. Bcl-2 expression in breast cancer tissue significantly correlated with histologic grade, tubule formation, nuclear pleomorphism, mitotic count, estrogen receptor, and distant metastasis. Our results suggest that beclin-1 might play a role in the inhibition of the development of breast cancer and that inhibition might be due to an interaction with bcl-2 protein.