Abstract
Spontaneous cardiac and renal lesions in APA hamsters were examined histopathologically. Myocardial degeneration, valvular thickening, coronary arterial degeneration and increase in heart weight were common in old hamsters. These changes, which suggest cardiac failure, seem to be related to cardiac thrombosis which predominantly affected the left atrium and was found in over 40% of each sex over 16 months of age. Neither glomerular amyloidosis nor arteriolar nephrosclerosis was detected. In general the histopathology of renal lesions in APA hamsters resembled that of the condition known as glomerulonephrosis in rats. Renal lesions occurred more frequently and more severely and developed more rapidly in females than in males. There was no apparent correlation between cardiac thrombosis and renal disease.