On review of the histology of 1050 primary breast carcinomas, 103 cases of infiltrating lobular carcinoma were identified and clinical and survival data collected in each case. The tumours were then separated into four groups on the basis of histological pattern and these groups shown to have significantly different survival times. Assessment of the presence of in situ carcinoma, elastosis and intracytoplasmic lumina was performed in each case and the effect of these features on survival investigated. In addition to stage of disease at presentation, the major significant factor in predicting survival of patients with this type of invasive carcinoma is histological type.