To establish prognostically useful pathologic features for infiltrating lobular carcinoma, histologic pattern, nuclear Grade 1 or 2, lymphatic invasion, the presence and extent of lobular carcinoma in situ, estrogen and progesterone receptor status, axillary lymph node status, tumor size, and pathologic stage were assessed as prognostic variables in 92 cases of infiltrating lobular carcinoma. Clinical follow-up was obtained (mean duration, 5.2 yr), and patients were classified as alive with no evidence of disease, alive with disease, or dead of disease. Recurrence (alive with disease and dead of disease) was associated with axillary lymph node metastases (P = 0.04), tumors measuring > 1.0 cm (P = 0.008), and pathologic Stage III/IV disease (P = 0.033). Survival (no evidence of disease and alive with disease) was associated with Stage I/II disease (P = 0.003). Statistically insignificant associations with disease recurrence or survival follow: infiltrative pattern (classical, alveolar, solid, mixed), nuclear grade, lymphatic vessel invasion, presence of lobular carcinoma in situ, extent of lobular carcinoma in situ (< 25% or > or = 25%), and hormone receptor status. Many of the prognostic features used in ductal carcinoma do not appear to be applicable to infiltrating lobular carcinoma. However, tumor size, axillary node status, and pathologic stage are prognostically useful in infiltrating lobular carcinoma.