In order to determine if intraoperative ultrasound (US)-guided excision is a feasible procedure, we prospectively studied 15 female patients between July 1996 and December 1998 for US-detected nonpalpable breast lesions. Intraoperative US was used by the operating surgeon to identify the lesion, guide its excision, and evaluate the specimen to document complete removal. A control group of 15 female patients with mammographically detected nonpalpable lesions was used for comparison. These patients underwent preoperative needle localization, excision of the lesions, and specimen radiographs. Age, size of the lesion, total excised tissue volume, and operative time were documented in all cases. Fifteen patients aged 20-83 years (mean 51) underwent US-guided excision, which adequately localized all lesions, and excision was successful in all patients. Specimen US documented the lesion in all cases. Lesion size ranged from 0.7 to 2 cm (mean 1.1) and the total excised tissue volume averaged 30 cc. Mean operative time was 53 minutes (range 30-75 minutes). The 15 patients of the control group ranged in age from 32 to 82 years (mean 61). Excision was successful in all cases. Lesion size ranged from 1 to 2.5 cm (average 1.5) and the average excised tissue volume was 35 cc. Mean operative time was 50 minutes (range 30-75 minutes). There were no statistically significant differences between the two groups with regard to age (p = 0.2), operative time (p = 0.5), and total excised tissue volume (p = 0.5). The size of the lesions did have a statistically significant difference (p = 0.01). There were no perioperative complications. In conclusion, US-guided excision of nonpalpable breast lesions is a feasible and effective technique. US documents results immediately, is of minimal discomfort to the patient, avoids the need for preoperative localization, allows the entire procedure to be performed in the operating room, does not require radiation, and provides the surgeon with a useful alternative in selected cases.