In a six year period up to the end of December 1985 fine needle aspiration cytology specimens of the breast were obtained from 562 apparently healthy women invited to participate in a breast cancer screening programme. Of these, 397 had a biopsy and 173 cancers were confirmed histologically. For the diagnosis of cancer, the procedure was less successful than in symptomatic cases. The main factors influencing success were the aspirator, the small size of many cancers, and the occult nature of the lesions seen only on mammography. Retrospective analysis of the figures shows that combining the results of FNA cytology in a triple assessment with physical and mammographical findings for restricted selection means that the number of benign biopsy specimens could be reduced considerably.