Four hundred and thirty-one patients with renal cell carcinoma treated at Jikei University and its related institutions from 1957 to 1988 were studied as to tumour size in relation to clinical characteristics (age, sex ratio, affected side, symptoms), prognostic factor (fever, weight loss, anaemia, elevation of erythrocyte sedimentation rate), pathological staging, pathological grading, and survival. The treated patients were divided into 4 groups on the basis of tumour size (group A; under 3.0 cm, group B; 3.1 to 5.9 cm, group C; 6.0 to 9.9 cm, group D; over 10 cm in diameter). At the time of operation, there were 22 cases (5.1%) in group A, 121 cases (28.1%) in group B, 209 cases (48.5%) in group C, and 79 cases (18.3%) in group D. In studying the clinical factors of age, sex ratio, and affected side, no relationship with size was detected. As for the symptoms, the larger the tumour, the more frequent the symptoms of urinary tract (haematuria, pain, and palpable mass). This tendency was especially marked in the cases of group D (over 10.0 cm in diameter). In addition, no relationships were observed between the rate of haematuria and the symptoms of extraurinary tract in each group. As for the prognostic factors (fever, weight loss, anaemia and the elevation of erythrocyte sedimentation rate), there was an obvious tendency for a positive reaction of these factors in the cases of groups C and D (over 6.0 cm in diameter). As for the distribution of stage and grade in each group, a higher stage and grade were observed with large sized tumours.(ABSTRACT TRUNCATED AT 250 WORDS)