Fine needle aspiration biopsy for cytological examination (FNAC) is becoming increasingly accepted as a means of tissue diagnosis in breast disease. This study examines the feasibility and accuracy of FNAC in 'immediate reporting' by a consultant cytopathologist in a busy breast clinic. Over a 2-year period, 884 cytology reports were analysed. An initial clinical report and subsequent final cytological diagnosis was made. Fine needle aspiration provided adequate material for cytological evaluation in 635 of the 884 biopsies (71.6 per cent) and this proportion was greater when discrete lumps were considered (463 of 562 biopsies = 82.4 per cent). In diffuse and cystic disease, however, the adequacy of specimens was reduced: 50 per cent and 65 per cent respectively. On immediate reporting the diagnostic sensitivity for all patients was 88 per cent (discrete lumps only, 92.5 per cent) and the specificity was 99.8 per cent (discrete lumps only, 100 per cent). FNAC retains its diagnostic accuracy when immediate reporting is employed and this study demonstrates that this technique can be used in making a diagnosis in patients with breast disease.