The grading of gastric epithelial dysplasia has been studied by means of computer aided morphometry. Measurements of histological features were made on segments of epithelium from 38 selected cases of dysplasia graded by subjective assessment. The measurements were statistically compared with the subjective scores using discriminant analysis. The measurements were found to provide significant discrimination between all groups. Nuclear size proved to be the main discriminating variable. Prediction of the likely group membership of individual cases was possible using classification equations derived from the discriminant analysis. Classification of the original data set revealed prediction errors which suggested a bias against diagnosis of dysplasia. As a result of this study reliable, repeatable and objective gradings of gastric epithelial dysplasia can be obtained by inexperienced persons with an accuracy approaching that of a skilled pathologist.