OBJECTIVE:To discover potential differences in known prognostic factors of renal adenocarcinoma in patients under 40 years of age. PATIENTS AND METHODS:A series of 246 patients with renal adenocarcinoma included 17 patients 40 years. Both groups were analyzed for sex, tumour size, histological characteristics and stage, examining the relative proportions within each group and looking for an association between those sets of data and age. RESULTS:No statistically significant associations were found, although it should be noted that in some cases data is incomplete. A larger proportion of low stages at least locally and a greater proportion of granule cell tumours was found in patients 40 years-old compared to those over 40. CONCLUSIONS:Existence of differences in the biological and histological characteristics of renal adenocarcinomas that develop at a younger age is not unlikely. The analysis of each factor and the survival rates in larger series should elucidate these questions, which will also be of interest to improve our understanding of the histogenesis of this type of tumours.