All cases of primary breast carcinoma seen at the George Washington University Medical Center between 1971 and 1975 and between 1981 and 1986 were reviewed, and examples of pure and mixed infiltrating cribriform carcinoma (ICC) were identified. The relative frequency of ICC did not change significantly from the earlier to the later study period. As previously reported by Page et al, there was a tendency for ICC to be associated with foci of tubular carcinoma and of intraductal carcinoma (often but not always of cribriform type). Pure ICC (defined as showing no other infiltrating carcinoma type), predominant ICC with lesser amounts of infiltrating carcinoma of any other type and any quantitative combination of ICC and tubular carcinoma metastasized to axillary lymph nodes frequently, but almost never to more than three nodes, in contradistinction to tumors composed of infiltrating duct carcinoma (IDC) not otherwise specified and less than 50% ICC, and a control group of IDC, which significantly more often involved four or more nodes. ICC cases were estrogen-receptor-positive in 100% and progesterone-receptor-positive in 69% of the cases. Five-year survival rates for eligible cases were 100% for pure and greater than or equal to 50% ICC, 88% for less than 50% ICC, and 78.3% for the IDC controls. ICC is a histologically and clinically distinctive type of mammary carcinoma that should be separated from IDC and other tumor types.