A retrospective study of 65 patients with unpalpable breast cancer revealed by microcalcifications on mammography showed that 18 had presented with infiltrating epithelioma. The contralateral epithelioma was revealed by mammography. Three deaths from metastases had occurred in this group. The 65 carcinomas discovered by mammography were treated by excision of the microcalcified area. This was followed by mammectomy in 34 cases and by irradiation in 25. Close surveillance only was suggested in 6 cases. Histological studies showed 6 lobular carcinomas in situ and 59 duct epitheliomas, 26 of which were infiltrating. The prognosis of isolated duct epitheliomas is highly favourable, and no dissemination was observed. The 2 local recurrences observed after secondary irradiation concerned infiltrating epitheliomas; these patients are now alive without sign of recurrence after mammectomy. After conservative treatment (tumorectomy followed by irradiation), no recurrence was observed among patients with non-infiltrating duct carcinomas.