The purpose of the present research was to detect and report the DNA content variation, the area covered by Feulgen-stained chromatin and the packing degree of the chromatin in clinical cases of human renal carcinomas (HRC). Scanning microphotometry was carried out on slides prepared from en bloc Feulgen-stained and squashed material. Accurate control procedures were performed using chicken erythocytes, normal human neutrophils and control kidney cell nuclei. It could be demonstrated that the HRC nuclei displayed polyploidy originated from hypodiploid stem cells. Micronuclei were detected exhibiting about 2pg DNA. Tumor cell nuclei showed larger areas of Feulgen-stained chromatin related to a decondensation process. Reduction of condensed areas was followed by higher values of average absorption ratios (AAR = average absorption of the condensed chromatin/average absorption of the entire stained chromatin), meaning that the condensed regions of the chromatin (CC) in these cases were more condensed than the correspondent CC of normal cells.154945961