This research was performed on 66 autopsy reports of kidney cancers and 58 autopsy reports of prostate cancers. Two alternative hypotheses were tested, i.e., whether metastases spread at random from the primary tumor throughout the body or whether metastatic spread occurs in steps, referred to as cascade spread, requiring 1 or more disseminating sites. In cancer of the prostate 2 disseminating sites exist, i.e., bones and lungs. Metastases from the primary tumor appear first in the skeleton and then in the lungs. In cancer of the kidney the lungs are the major disseminating site. The lymphatic areas did not seem to play a major role in the dissemination of both cancers. The presence of metastases in the lymph nodes depended on the presence of carcinomatous cells in key sites, i.e., the skeleton and lungs. These results should be interpreted with caution. Considerations were proposed for future research.