An 11 month-old squirrel monkey that died after one week of illness, characterized by anorexia, lethargy, pale mucosae, and dehydration was presented for post-mortem examination. A large retroperitoneal abscess with adhesions to the colon was found on necropsy. Culture of the pus from the abscess on blood agar and MacConkey agar, resulted in heavy growth of Klebsiella Pneumoniae. The significance of this organism as a cause of morbidity and mortality in non-human primates with particular reference to squirrel monkeys is discussed.