To reduce the need for excisional biopsies in the diagnosis of breast masses, the accuracy of core needle biopsy (CNB) was determined in a university hospital setting. 150 consecutive women with solitary palpable breast masses underwent CNB over a 2-year period. Histological diagnosis was established, and in the case of cancer the type, grade and estrogen and progesterone receptors were determined. CNB findings were compared with those independently obtained from the subsequently excised lesions. There were 103 malignant and 47 benign lesions. CNB diagnosed 136 lesions (90.7%) correctly. Fourteen biopsies were inconclusive. Histological type was correct in all cases and grading in 83.5%. Correct hormone receptor status was obtained in 97.1% of cases for estrogen and 91.3% for progesterone. Diagnosis of histological type, grading, and hormone receptors obtained from CNB material is a safe way to analyze palpable breast lesions and therefore a useful tool to select patients for preoperative treatment.