Previous studies have shown that 80-90 per cent of cases of atypical hyperplasia of the endometrium do not progress to cancer. Criteria to predict the outcome in an individual patient with hyperplasia are lacking, and hysterectomy is the usual (over)treatment in order to avoid a 10-20 per cent chance of confrontation with cancer later on in the course of the disease. A recent study has shown that using a nuclear morphometric classification rule, 15 per cent of patients without progression can be accurately separated from patients with progression. However, as it is unlikely that nuclear morphometrical features are the only morphological factors reflecting the outcome of the disease, other quantitative parameters describing the architecture of the glands have also been studied for their potential value in selecting patients who will progress to cancer. In total, 10 nuclear features and 12 glandular architectural features were studied in 39 cases of atypical endometrial hyperplasia. Among these cases, seven (18 per cent) progressed to cancer. Using linear stepwise regression analysis and discriminant analysis, the volume percentage stroma and the standard deviation of the shortest nuclear axis are the best discriminators, although the outer surface density of the glands also adds to the discriminating power. The volume percentage stroma is the best single prognosticator; this feature is highly reproducible. In total, using these combined architectural and nuclear morphometrical features, 20 of the 32 cases without progression were separated from those who subsequently progressed (62.5 per cent). This is a considerable improvement over nuclear morphometrical features alone (15 per cent separated).