Three basic cytologic variants were identified among cases of infiltrating ductal carcinoma of the breast (NOS). These variants were found to have different distributions among patients surviving 25 years after mastectomy, compared with matched short-lived control subjects. Multivariate analyses indicated that recognition of these cytologic variants enhanced the prognostic value of tumor grade and blood vessel invasion. Patients with tumors designated here as histologic type C, which others have called invasive cribriform carcinoma, appear to have a higher probability of long-term survival than patients with other histologic subtypes. Since they account for approximately 20 per cent of 25-year survivors, they should be distinguished from patients with other types of infiltrating ductal carcinoma (NOS).