A retrospective study was carried out in five main General District and Teaching Hospitals in Tehran (18 general surgical wards) to investigate breast cancer in Tehran, Iran. All patients who have had breast pathology during 1985-95 were reviewed. For each patient the following data were extracted from case records sex, age, type of disease (based on ICD-10 and ICD-O), breast cancer pathology, tumor size, lymph node involvement, pathological staging (based on TNM system), type of surgery, mass location and the affected side of breast. In all 3085 records were reviewed. Of these, in 903 cases the final diagnosis was breast cancer. The mean age of breast cancer patients was 47.1 (SD=12.3) y and the age-adjusted analysis showed that the observed number of breast cancer cases in the age group 40-49 was higher than expected (P<0.001). The majority of patients (71%) were patients with infiltrating ductal carcinoma, 70% had advanced disease (Stage III), and in 51% of cases the tumour was more than 5 cm in size. Finally it was found that two-third of patients (76%) underwent modified radical mastectomy. Although this study does not address true incidence, but rather frequency, the findings suggest that the Iranian breast cancer patients are relatively younger than their western counterparts and mostly have locally advanced disease. In terms of breast cancer screening programs, these findings have some implications for public health professionals in Iran.