The prognostic impact of DNA ploidy, MIB-1 and p53 was evaluated in relation to clinical and histopathological features in surgical stage I endometrial carcinoma (n = 284) and in the histopathological endometrioid subgroup (n = 257). Tumour material from 284 consecutive patients was analysed regarding image cytometric DNA ploidy and the immunohistochemical MIB-1 and p53 expression. Twenty-four tumours relapsed. In univariate analysis, histopathological subgroup (endometrioid vs. non-endometrioid), grade, DNA ploidy and p53 were highly significant prognostic factors (p < or = 0.001). MIB-1 was also significant (p = 0.039). In the endometrioid subgroup only DNA ploidy and p53 were significant (p < 0.001). In multivariate analysis of the entire material, ploidy and histopathological subgroup retained their significance (p = 0.001, p = 0.004), whereas only ploidy was significant in the endometrioid subgroup (p = 0.001). DNA ploidy was the strongest predictor of relapse-free survival and the only independent prognostic factor in the endometrioid subgroup.