Cell kinetic information is an important adjuvant to histologic grading and to stage in some malignant tumors. Some studies have shown that in endometrial carcinomas, flow cytometric S-phase correlates with known prognostic parameters. In the current study, the expression of silver-stained nucleolar organizer regions (AgNORs) and MIB-1 (ki-67-paraffin) was assessed on paraffin sections in 112 endometrial adenocarcinomas of endometrioid type (EC) (49 hormone users, 63 nonusers). The AgNOR morphology correlated significantly with MIB-1, mitotic count, and nuclear and architectural grade, but not with stage or previous hormone treatment. MIB-1 correlated with all the above parameters except myometrial invasion and stage. Only myometrial invasion and stage correlated with short-term outcome; in such cases tumors from hormone users and nonusers were pooled. The median MIB-1 value was significantly lower in EC from hormone users compared with EC from nonusers; moreover, when tumors from hormone users and nonusers with poor outcome were examined separately, only 29% (four of 14) of the tumors expressed MIB-1 less than the medians in the respective groups, indicating that a prognostic cutoff point may be different in the two groups. Because hormone replacement therapy is very common, this observation has implication for future studies of growth fraction in EC. This is the first study to show that AgNOR morphology is significantly correlated with other markers of growth fraction and histologic grade.