The aim of this study was direct comparison of clinicopathologic features in male and female breast cancer patients. The study included 100 male and 500 female patients with pathohistologically confirmed breast cancer, who were treated at the University Hospital for Tumors in Zagreb, Croatia, between 1970 and 1990. The results revealed significant sex-related differences in the following characteristics: patients age at diagnosis (36% vs. 66% below the age of 60, respectively, p < 0.001), delay in treatment (29% vs. 58% within the first 3 months, p < 0.001), tumor size (45% vs. 58% up to 5 cm, p < 0.001), number of affected regional lymph nodes (74% vs. 87% up to 5 nodes, p < 0.01), TNM-stage distribution (49% vs. 56% in stages I-II, p < 0.001), estrogen receptor values (69% vs. 32% > 10 fmol/mg protein, p < 0.001) and progesterone receptor values (67% vs. 48% > 10 fmol/mg protein, p < 0.05). No significant sex-related differences in breast cancer patients were found regarding histologic grade of malignancy (males: grade I-36%; II-34%; III-30%; females: grade I-33%; II-36%; III-31%), affected breast (left in 58% males vs. 50% females), and type of surgical treatment (modified radical mastectomy in 64% male vs. 61% female patients). This study confirmed the well-known facts that male breast cancer develops at an older age and with a much higher proportion of positive tumor hormone receptors. Furthermore, the authors found the male patients in Croatia to be insufficiently informed about the possibility of breast cancer development in male sex, which resulted in a significantly prolonged treatment delay and, consequently, higher TNM stage of the disease, bigger tumors and more affected lymph nodes at the time of diagnosis in comparison to female patients.