The value and accuracy of a scoring system applied to clinical examination, aspiration cytology and mammography has been assessed in the diagnosis of 224 consecutive 'new' patients attending a breast clinic with a breast lump. In 72 of 99 patients with breast cancer (80%) the scores were high enough to allow definitive surgery without formal histology; all were subsequently confirmed as breast carcinomas. Cytology proved the most accurate investigation with no false positives and a correct diagnosis in 146 of 148 adequate specimens (98.6%). This system reduced the frozen section rate by 74% and allowed for a more appropriate counselling of patients prior to mastectomy.