In a study of 70 patients with 75 histologically proven fibroadenomas of the breast, a biphasic peak incidence was recorded, initially in their late 20s to early 30s with a second unexpected peak in their late 40s to early 50s. These lesions averaged 2.8 cm in diameter, two thirds were located in the lateral quadrants of the breast, and 10 percent were multiple. There was a significantly higher incidence among nonwhite than white women when compared to census figures and hospital admission data. The corrected recurrence rate was 17 percent. An inordinately high number of patients under 40 years of age in this series were nonwhite. Family history demonstrates a significantly high incidence of breast disease of all types in first-degree relatives.