This study was carried out 1) to analyze the growth and clinical manifestations of renal adenocarcinoma; 2) to determine the presence of tumor, its malignant nature, size, local extent or distant spread and route of dissemination according to the imaging methods utilized, and 3) to determine the accuracy of the different imaging procedures, such as IVP, US, CT, and MRI, in staging renal adenocarcinoma. These objectives attempted to provide answers to the following questions: a) Are there currently substantial changes in the biological behavior of renal adenocarcinoma?, b) Does the route of tumor dissemination (direct infiltration through the capsule, lymphohematogenous, cancer embolus carried by the bloodstream to a distant location) affect the rate of progression to stages III and IV?, and c) What are the most relevant findings of the imaging methods that aid in determining the extent of the renal tumor?106 renal masses were evaluated; of these, 93 were renal adenocarcinomas. The diagnosis, clinical evaluation and preoperative staging were based on the clinical history, physical examination, symptoms and imaging methods (IVP, US, CT, and MRI) to assess renal morphological changes, presence of calcifications, mass effect, tumor mass ultrasound characteristics, densitometry or MR signal pattern, perinephric fat involvement, venous vasculature, involvement of renal fascia, locoregional lymph nodes or metastasis and distant neoplastic changes.A third of the tumors had a size greater than 10 cms and practically half were 5-10 cms in size. Calcifications were found in 47%; 85% were punctiform and showed a central location. 88% of the tumors showed areas of necrosis. Due to the presence, in most of the cases, of a viable tumor, necrosis, calcification or cystic degeneration, the adenocarcinomas showed a very inhomogeneous ultrasound pattern and with varying degrees of vascularization on CT volumetric assessment. Invasion of perinephric fat and tumor fibrous septae were found in 65% on CT evaluation, although MRI was particularly sensitive in detecting fat infiltration in the early stages of perinephric involvement, venous thrombosis, involvement of adjacent and distant organs and tumor hemorrhagic changes.In determining the biological behaviour of renal adenocarcinoma, preoperative staging of infiltration and prognosis, US, volumetric CT and MRI are currently the diagnostic methods with the highest accuracy, specificity and sensitivity. These diagnostic methods allow early detection of tumors thereby making them potentially curable. Lymphatic drainage of the tumor may be determinant in its more or less rapid progression from Robson stage II to IIIa and IIIb, and thereafter to stage IV. CT and MRI showed a higher accuracy for tumor detection, localization, determining local extent, tumor characterization and staging. Detection of a tumor pseudocapsule comprised of reactive fibrous tissue and compact renal parenchyma by CT or MRI allows determination of the borders of the renal tumor. Lymph node involvement radically changes the prognosis and survival in renal adenocarcinoma.