The DNA content and nuclear measurements of five groups of endometrial proliferations--proliferative endometrium (PE), simple hyperplasia (SH), atypical hyperplasia (AH), well-differentiated carcinoma (WDC), and poorly differentiated carcinoma (PDC)--were compared using 14 descriptors in a stepwise discriminant analysis. Classification using the discriminant rules agreed with the pathologic interpretation for 78% of the specimens. All PEs were assigned to the correct group, and 97% of benign endometria and carcinomas were correctly classified as benign or malignant. Only two of 39 hyperplasias (5%) were misclassified as malignant, and only one of 36 carcinomas was classified as benign. In the difficult distinction between AH and WDC, using all descriptors for the five groups, only 68% of the AH and 60% of the WDC classifications were in agreement with the pathologist of record. However, when discriminant rules addressing only AH and WDC were used, 37 of 39 AHs and WDCs were in concordance. This suggests that a morphometric distinction between AH and WDC is feasible.