PURPOSE: Infiltrating lobular carcinoma of the breast was known to have a high incidence of multicentricity and bilaterality in patients. We analyzed the clinical features of infiltrating lobular breast cancer. MATERIALS AND METHODS: We studied 29 patients with infiltrating lobular carcinoma of the breast, from Jan. 1980 to Mar. 1997 in the Department of Surgery, Seoul National University Hospital. RESULTS: The age of the patients ranged from 32 to 71 years with an average of 45.2 years. The main complaining symptom was a painless mass. The diameter of the tumor ranged from 0.7 to 7 cm with a mean size of 2.8 cm. The axillary lymph node was positive for malignancy in 12 cases. The number of multicentric breast cancers were 7 cases (24.1%), and the number of bilateral breast cancers were 3 cases (10.3%). The estrogen receptor was positive in 66.7%, and the progesterone receptor was positive in 75% of the cases. There were one local recurrence and three distant metastases during a mean follow-up period of 4.5 years. The 5-year survival rate and 5-year disease free survival rate were 89.6% and 88.6%, respectively. CONCLUSION: Infiltrating lobular breast cancers are at greater risk of developing multicentricity and bilaterality than nonlobular breast cancers. Careful program of frequent follow-up examinations and thorough histopathological studies are needed for patients with infiltrating lobular breast cancers.