Components of the pRb1 pathway play a pivotal role in regulating the G1/S transition in the cell cycle. This study investigated the association between pRb1-cyclin D1-cdk4-p16INK4A pathway alterations and the clinical and prognostic utility for women affected by primary uterine endometrial adenocarcinoma (EC). The study population consisted of 50 cases of EC patients who were investigated for RB1 and CDKN2A (alias p16INK4A) gene alterations, as well as for the expression pattern of pathway proteins. Altogether, pRb1 pathway alterations were noted in 54% (27 of 50) of ECs, and more frequently in advanced-stage uterine carcinomas (P=0.024, Fisher exact test). Loss of heterozygosity abnormalities in RB1 and CKDN2A coexisted with altered cyclin D1-cdk4 complex immunoreactivity only in 2 patients, both less than 50 years of age. With respect to pRb1 pathway alterations, however, the recurrence rate was not significantly different (P=0.477; log-rank test). Our results suggest that the progression of uterine endometrial adenocarcinoma is generally accompanied by increased frequency of pRb1 pathway alterations. Alterations of the retinoblastoma pathway may not be necessarily associated with the recurrence of EC.