A total of 425 wire localized biopsies for non-palpable breast lesions found by screening (n = 169) or clinical (n = 256) mammography between 1986-1990 are reviewed with reference to the biopsy success rate with different localization techniques, the positive predictive value of the mammographic findings and the staging and treatment of carcinomas in the clinical and screening groups. Specimen radiographs were available for review in 371 cases and confirmed the removal of the lesion in 90.6%, were indeterminate in 4.8% and were negative in 4.6%. Some 95% of the failures occurred in mammography-guided localizations using the Kopans hookwire. In later years this wire was replaced with th Homer retractable needle/wire system, with a 99% success rate. The Kopans wire was found to be accurate in ultrasound (US)-guided procedures, which were tolerated very well with no complications, as compared with a 10.2% rate of vasovagal reactions in mammography-guided procedures. The success rate of the localizations performed under general anaesthesia was 93.7%, as compared with 80.2% of the localizations performed under local anaesthesia. A more clearcut improvement of the success rate (from 66.7% in 1986-1987 to 99% in 1990) was seen over the years with growing experience and the development of teamwork between radiologists, surgeons and pathologists. The histological diagnosis was malignant in 27% of cases. The positive predictive value for malignancy improved from 21% to 32% from 1986 to 1990, due mainly to an increase in the screening group. A total of 71% of the carcinomas found were of stage 0 (TisN0M0) or I (TIN0M0) indicating a good prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)