A pilot study was undertaken to determine the expression of certain nuclear features in prostatic lesions. Twenty cases, 5 of hyperplasia and 5 each of carcinoma, Mostofi grades I-III, were selected as a training set, and an additional 20 cases were used as a test set, including 5 cases of hyperplasia and 5 cases each in Mostofi grades I-III. Images of hematoxylin and eosin-stained, 4-microns paraffin sections were obtained with a JVC BY-110 three-color camera and digitized by an IBM personal computer with a Matrox MVP-AT/NP imaging board. Thirty nuclei for each case from the training set, for a total of 600 nuclei, and 10 nuclei for each case from the test set, for a total of 200 nuclei, were analyzed by quantitative cytometric software on a SUN 3/60 workstation. A linear discriminant model was used for statistical analysis. One hundred percent of the hyperplasia group, 98% of the low grade group, 92% of the medium grade group and 82% of the high grade group were classified correctly in the test set with an overall success rate of 93%. Statistically significant chromatin texture features included heterogeneity, condensation, margination, run length nonuniformity, long run emphasis, gray level nonuniformity and inertia. Area, roundness and staining intensity (total extinction) were also significant. The results with standard hematoxylin and eosin-stained tissue sections were similar to those previously obtained with Feulgen-stained material. These results indicate that routine hematoxylin and eosin-stained material offers consistent diagnostic clues.