The results of the first 1,500 cytological diagnoses of fine-needle breast aspirates performed at Groote Schuur Hospital Breast Clinic are compared with the histological diagnoses of Tru-cut and excision biopsies of the same lesions. A cytological diagnosis of malignant disease was made in 358 cases, 349 of which were confirmed histologically. The 10 false-positive and 1 false-negative diagnoses are discussed. The reliability of diagnosis in the first 500 cases is compared with that in the second and third 500 cases. There were no false-positive diagnoses in the last 500 cases, and only 3 in the second 500 cases compared with 7 in the first 500 cases. Similarly, the 1 false-negative diagnosis was made in the first 500 cases. The results confirm the reliability of fine-needle aspiration biopsy cytology as a diagnostic technique. The number of incorrect diagnoses decreases as experience with the technique increases.