The effectiveness of ketamine and xylazine as an immobilizing combination for muskrats (Ondatra zibethicus) was evaluated. Eleven muskrats were intramuscularly injected using a high (n = 7) or low (n = 4) dosage of a 20:1 mixture of ketamine (12 or 20 mg) and xylazine (0.6 or 1.0 mg) in Carlton County, Minnesota (USA) from 1 to 4 May 1995. Mean (+/- SD) induction times for muskrats receiving a high dosage (6.5 +/- 2.6 min) or low dosage (7.0 +/- 1.6 min) was similar (P = 0.71). In contrast, muskrats receiving a low dosage recovered sooner (37.0 +/- 15.1 min) than muskrats receiving a high dosage (62.2 +/- 15.6 min) (P = 0.04). There was a positive linear relationship (r2 = 0.75, P = 0.02) between the amount (mg/kg) of ketamine-xylazine injected and recovery time but not between the amount injected and induction time (r2 = 0.49, P = 0.18). Heart rate, respiratory rate, and body temperature were similar (P = 0.20 to 0.62) between high and low dose groups. No mortality occurred nor were short-term adverse effects observed in recaptured individuals. I conclude that a 20:1 mixture of ketamine-xylazine is a safe and effective immobilization agent for muskrats when conducting non-surgical field procedures. Immobilizing muskrats with 15 mg/kg ketamine and 0.75 mg/kg xylazine should provide about 10 min of handling time before arousal and allow full recovery in < 60 min.