Lobular carcinoma in situ (LCIS) is generally treated by conservative surgery alone and less often by mastectomy. We report our experience using conservative surgery and whole breast irradiation (WBI) for the treatment of patients with LCIS. From 1980 to 1992, 25 women with a median age of 54 years underwent lumpectomy (20) or quadrantectomy (5) and WBI (median dose: 52 Gy) for treatment of their LCIS. Five cases had palpable lesions, 19 were found by mammography alone and one case was found due to nipple discharge. Twelve women received tamoxifen at 20 mg/day for 2 years. With a median follow-up of 153 months (range 58-240), only one local recurrence was observed. The global rate of bilateral carcinoma was 17.6% (two synchronous and one metachronous). Until now, no case of LCIS treated by lumpectomy and radiation therapy has been reported in detail in the literature. After biopsy alone for LCIS, a subsequent infiltrating carcinoma occurs in approximately 15% of cases. Thus, classical radiosurgical therapy should represent an interesting alternative both for limited surgery alone and mastectomy, both of which have been proposed as sole treatments for LCIS.