In 110 consecutive, medicolegal autopsies of young and middle-aged women (range 20-54 years) the breasts were examined by an extensive histopathologic method and by correlative specimen radiography. Malignancy was found in 22 women (20%) of which only one was known to have had clinical invasive breast cancer (IBC). At autopsy 2 women had IBC (2%), the remaining in situ carcinoma (in situ BC) of microfocal type (18%), i.e. 15 (14%) intraductal carcinomas (DCIS), 4 (3%) lobular carcinoma in situ (LCIS) and one (1%) both DCIS and LCIS. Forty-five per cent of the women with malignancy had multicentric and 41% had bilateral lesions. Forty-five per cent of all histologically confirmed malignant lesions were identified by specimen radiography. Adenosis, benign epithelial hyperplasia, papilloma and duct ectasia were positively associated with malignancy. In addition malignancy was significantly more frequent among women aged more than 40 years, with late age at first full-term pregnancy, with alcohol abuse and with steatosis or cirrhosis of the liver. The results suggest that clinically occult in situ BC are frequent in young and middle-aged women.