Objective -To characterize the clinical presentation, management, and in-hospital outcomes of dogs and cats diagnosed with acute congestive heart failure (CHF). Design -Retrospective study of animals seen between January 2007 and May 2008. Setting -Emergency service at a university teaching hospital. Animals -Ninety dogs and 55 cats with CHF. Measurements and Main Results -Patient characteristics, including age, clinical signs, clinicopathologic abnormalities, diagnostic testing, and outcome were recorded. Forty-eight of the animals already were receiving cardiac medications at the time of presentation. The most common diseases represented were chronic valvular disease and cardiomyopathies. Cats had significantly lower median body temperature at admission compared with dogs (Po0.001). The most common abnormalities were elevated lactate (64%), elevated BUN (52%), hypochloremia (31%), hyperglycemia (27%), and elevated liver enzymes (26%). Many of these became even more prevalent during hospitalization. One hundred and sixteen animals were discharged from the hospital, for a survival rate of 80%. There was no survival difference between dogs and cats (P 5 0.39). Dogs that developed hypokalemia during hospital stay (P 5 0.04) were more likely to survive compared with those without hypokalemia and initial body temperature was lower for those cats that did not survive (P 5 0.02). Of those that did not survive, the majority were euthanized (n 5 25), while 4 dogs died. Conclusions -Dogs and cats presented to the emergency service with CHF had a high survival rate. In cats, initial body temperature was lower for those cats that did not survive. Although clinicopathologic abnormalities were common in both species, only dogs with hypokalemia had improved survival to hospital discharge.