A syndrome in male cats analogous to chromatin-positive Klinefelter's syndrome 
in human males has been demonstrated. The physical characteristics which 
suggested an abnormality of chromosome number in cats were "calico" or 
"tortoise-shell" coat colors in a male. Buccal mucosal smears were found to have 
"female-type" patterns in two out of 12 such male cats screened, and these two 
were found to have a diploid chromosome number of 39 rather than the normal 38. 
Testicular biopsy performed on one revealed an abnormal pattern; no gonadal 
tissue was found in the other cat with an abnormal chromosome number. These 
findings indicate that the cat, in addition to the mouse, is available for 
experimental study of chromosome number abnormalities.