DNA analysis was performed on fresh frozen samples of the primary tumor in 32 patients with renal carcinoma (13 with apparently localized disease and 19 with metastases at presentation). A comparison of ploidy with staging and standard histologic variables was performed. None of the patients who presented without metastases died of disease during the follow-up period. Eleven of 13 patients of this group had a diploid/near diploid pattern, and metastases developed in only one patient. Patients with metastatic disease and a diploid/near diploid DNA content had a significantly better survival rate than those with aneuploid primary tumors. Statistical analysis showed that grade and ploidy contributed significant but independent prognostic information. We concluded that DNA content is a useful prognostic factor in renal carcinoma.