Abstract
A variety of human tumors has been carried exclusively in rodent heterotransplant passage for periods ranging from 7 to 11 years. They have preserved human karyotypes and in general have continued to show the microscopic pattern of the original tumors. H. Emb. Rh. #1 has a morphologically normal male karyotype. H. S. #1 has 47 chromosomes with the same stemline karyotype in almost all analyzable cells, but many chromosomes are distinctly abnormal, with 5 of the metacentrics possessing satellites. ME 1 has a probable stemline of 123 chromosomes and can be interpreted as having the same karyotype in most stemline cells.