We retrospectively reviewed surgical biopsy findings of lesions diagnosed as radial scars (RS) at stereotactic core-needle biopsy (SCNB). RS was diagnosed in 52 of 1415 (3.7%) consecutive mammographically detected lesions that underwent 14-gauge automated SCNB. Subsequent surgical biopsy findings were available for 43 lesions in 41 women constituting the study group. Of these 43 lesions, histopathological analysis of the surgical specimen yielded RS in 27 (63%), RS plus atypical ductal hyperplasia (ADH) in 8 (18%), RS plus carcinoma in five (12%), and only carcinoma in three (7%). Carcinomas underestimated at SCNB (n=8) were two in situ carcinomas, two invasive ductal carcinomas not otherwise specified, and four tubular carcinomas. A statistically significant difference (P=0.02) was found between the mean pathologic size of RS without carcinoma and of RS containing carcinoma. Mammographic features could not be used reliably to predict the presence of carcinoma at excision of lesions diagnosed as RS at SCNB. The results suggest that the diagnosis of RS at 14-gauge SCNB of mammographically detected lesions is an indication for surgical biopsy because of the high prevalence of carcinoma in these lesions.