A total of 38 renal adenocarcinomas with isolated invasion of the renal vein and maximum local extension to perirenal fat, operated over a 20-year period and with long-term follow-up were reviewed. They were divided in two subgroups, 12 T1-2,N0,M0,V1 cases were compared to 54 T1-2,N0,M0,V0 cases treated in the same period of time, but no significant differences were found in survival (83% and 68% at 5 and 10 years for V1 versus 80% and 64% for V0); and 26 T3,N0,M0,V1 cases compared to 49 T3,N0,M0,V0, again with no significant difference found in survival (40% at 5 years and 26.5% at 7 years for V1, versus 38.5% and 34% for T3V0). When comparing the survival rate of T1-2,N0,M0,V0-1 with that of T3,N0,M0,V0-1, the difference was significant (p). It is concluded that the isolated invasion of the renal vein and an equal locoregional extension of the tumour do not modify the prognosis for renal carcinoma, and that this parameter should be included in the new TNM classification of the isolated UICC, since when included within the T3b category it places cases with good prognosis (T1-2 V1) above cases with poor prognosis due to the existence of invasion of the perirenal fat (T3a).