Suspensions from lungs of infected cats inoculated intranasally into mice caused sickness and sometimes death. Suspensions of lungs of these mice produced the disease in kittens. Cultures obtained from lungs of the infected cats showed few bacteria or none and attempts at filtering with a Berkefeld filter gave irregular results[long dash]suggesting that the organism may be a virus. Staining revealed numerous bodies similar to those of psittacosis. The infection apparently spreads from cats to man, causing an atypical pneumonia. Complement-fixation tests are being worked out.