In this study histologic slides of 165 patients who were diagnosed as RCC between 1983 and 1993 were re-evaluated and each tumour was graded according to Thoenes, Fuhrman, Arner and Skinner's grading systems. According to Thoenes' system, patients with grade (G) 2 and 3 tumours had significantly shorter survival compared to patients with G 1 tumours. The survival difference between the subgroups of Fuhrman and Skinner's grading systems did not reach statistical significance. When the histologic differentiation was grouped as low grade (G 1&2) and high grade (G 3&4) tumours in Fuhrman and Skinner's systems, a statistically significant difference was noted between the groups in terms of survival.