In 36 patients with renal carcinoma ploidy and cell cycle analysis of the tumour tissues by flow cytophotometry were performed. Considering the tumour stages pT, pN, and M no relationship between stage and DNA distribution could be established. With reference to the histological grading, grade I tumours showed only euploid DNA distributions, whereas grade II and III carcinomas exhibited both euploid and aneuploid DNA patterns. Whether ploidy analysis is correlated with the prognosis of the tumour disease remains to be determined.