Systematic chromosomal studies in solid tumors have been scanty (excepting meningiomas), because of the fact that it is difficult to obtain tumor material at desired times and only in about 10--15% of the cases adequate chromosome preparations are suitable with a direct technique or short term culture. A few facts that emerge from the study of various solid tumors are as follows: 1. modal number of chromosomes in parimary tumors tends to be lower that of metastatic; 2. certain chromosomes and chromosome regions are more susceptible for breakage to oncogenic conditions, hence, there is non-random involvement of certain chromosomes in human neoplasia and 3. certain chromosome changes are more often associated with metastatic spread than others.