Of 8 tumors surgically extirpated from 8 patients with renal cell carcinoma, 7 were successfully processed in short-term culture by collagenase method, and 130 metaphases were extracted from these 7 tumors and were subjected to chromosomal analysis according to the G banding technique. As for karyotype, 4, 2 and 1 cases were mainly diploid, hypodiploid and aneuploid, respectively. The highest incidence of chromosome aberration was marked by #3 chromosome (5 of 7 cases of which 4 and 1 showed monosomy as clonal aberration and trisomy as non-clonal aberration, respectively). The commonest gain of chromosome was noted for #7 trisomy (4 of 7 cases). Two cases had already had metastases at the time of surgery, each showing #7 trisomy. Marker chromosome was noted in 6 of 7 cases. Structural chromosome aberration had a lesser incidence compared with numerical aberration; only clonal aberrations were long-arm aberrations (2q+, 6q+) of #2 and #6 chromosomes. Short-arm aberrations (3p-, 8p-) of #3 and #8 chromosomes were noted in one case each. 3p deletion, which is reported to be predominant in the literature, was noted only in one case. This was observed in triploid cells. However, all of metaphases showing 2q+ and 6q+ had concomitant #3 monosomy, and excess portions of #2 and #6 chromosomes were in good agreement with the band pattern of #3 chromosomal long-arm. Therefore, translocation of 3q12-qter in #2 and #6 chromosomes is supposed to lead to 3p deletion. A similar mechanism seems to be involved in the formation of marker chromosomes, suggesting the involvement of deleted #3 chromosome in marker chromosomes.