Background: The roles of breast conservation and surgical evaluation of the contralateral breast in the treatment of lobular carcinoma of the breast remain unclear. The aim of this study was to compare local recurrence, 5-year survival, and incidence of contralateral breast cancer in women with lobular carcinoma to that in women with infiltrating ductal carcinoma. Methods: Women with infiltrating ductal carcinoma (IDC) and invasive lobular breast carcinoma (ILC) diagnosed during the years 1984 to 1994 were identified through a statewide tumor registry. The women were divided into groups based on their histology and treatment (breast conservation or modified radical mastectomy). The incidences of contralateral breast cancer, local recurrence, and 5-year survival were compared within each histologic group and treatment category. Results: During the period 1984 to 1994, 4886 women were diagnosed with invasive lobular or ductal breast carcinoma. Of these, 316 (6.5%) had infiltrating lobular cancer. The 5-year survival rates were 68% and 71% for ILC and IDC, respectively (p = 0.5). The local recurrence rates were 2.8% and 4.3% for ILC treated with lumpectomy and axillary nodal dissection (LAND) and modified radical mastectomy (MRM), respectively, which were not significantly different from that obtained with IDC (LAND = 2.5%, MRM = 2.1%). The incidence of contralateral breast cancer during the period was 6.6% and 6.5% for ILC and IDC, respectively. Conclusions: Invasive lobular carcinoma can be safely treated with breast conservation with no difference in local recurrence or survival. In the absence of a suspicious finding on clinical or radiologic examination, routine contralateral breast intervention is not recommended. Published by Lippincott-Raven Publishers © 1997 The Society of Surgical Oncology, Inc.