During a period of 10 years, 2906 women (mostly asymptomatic) were referred to us for physical breast examination. Fine needle aspiration (FNA) was used to examine a nodule or a breast thickening in 860 of these patients. One hundred and ten of these patients also underwent a large needle biopsy (LNB) to add a pre-operative histological evaluation. LNB was performed with 18-20 gauge needles, without cutting the skin and without adding any significant pain or discomfort to that caused by FNA (aspiration needle biopsy, ANB). Diagnostic sensitivity for cancer was 89% for FNA and 100% for ANB. ANB allowed us to correctly identify two cancers with post-operative stage T1N0M-0, which were diagnosed pre-operatively as benign by FNA. The combination of the two needle aspiration techniques (FNA and ANB) allowed us to diagnose 51 of all the 54 cancers (95%). The predictive value of a diagnosis of definite malignancy was 100% for either FNA or ANB. The predictive value of a diagnosis of suspected malignancy showed a predictive value of 72% for FNA and 70% for ANB. Three benign nodules with pre-operative ANB findings of suspected cancer were correctly diagnosed by FNA. Of the 12 cancers with inadequate ANB findings, 11 were correctly diagnosed by FNA. Sixteen of the cancers correctly identified by ANB showed a post-operative size of 2 cm or less (ten cases) or no metastatic axillary lymph-nodes (nine cases).(ABSTRACT TRUNCATED AT 250 WORDS)