Abstract
Chromosome studies have been made of 2 human colonic tumour lines maintained as xenografts in immune-deprived mice. In both tumours human karyotypes were retained, although progressive changes occurred during serial passage. In one tumour, independent gain of a chromosome 19 was found in the stemline and 2 sidelines. In the other tumour there was selection for a sideline containing a particular deleted marker chromosome. The advantages of chromosome analysis in a xenograft system, both for the study of human solid tumour karyotypes and for monitoring the continued presence of the human genome, are discussed.