During 1958, 91 cases of breast carcinoma in women below 30 years of age were reported to the Swedish Cancer Registry. A histologic reexamination showed that 16 of these women had only benign proliferative conditions. Among the remaining 75 patients, two had noninvasive carcinoma, eight advanced carcinoma, and 65 operable invasive carcinoma. The carcinomas were characterized by little fibrous stroma and little or no elastosis. The survival rate of the patients with invasive breast carcinomas was similar to that in a total geographic material of all ages with breast carcinoma. The carcinoma was treated during pregnancy or within 1 year after delivery in 15 patients, with the same survival rate as for those whose carcinoma was not complicated by pregnancy.