RECENTLY, a chromosome abnormality found in three cases of lymphatic leukaemia in cattle was described1. This communication reports my latest findings concerning this abnormality. It appears that in Sweden cattle chromosomes have only once before been investigated using modern techniques. On that occasion Melander2 found the chromosome number in animals of the Swedish breed SLB to be 60; all autosomes were characterized by having strictly terminal centromeres. The existence of telocentric chromosomes has now been verified in several groups of animals including cattle3–6.