A geographically stratified sample of 25 small-animal practices administering at least six transfusions to dogs over the last 12 months was surveyed to determine how veterinarians obtain blood for transfusions, the direct costs of administering transfusions, and the impact of available blood on the management of critically ill dogs. The primary source of donor blood for each practice was a borrowed dog (12 practices) or in-house dogs kept on the premises (12 practices). Only one practice obtained blood from a nearby veterinary school. There was a wide variation in practices regarding testing for diseases and screening of donors. Thirty-six percent of practices surveyed did not screen dogs for infectious diseases or evaluate hematologic variables prior to blood donation. Twenty-four percent of the respondents evaluated the donors solely for the purposes of detecting microfilaria. The remaining 40% of the practices performed one or more of the tests generally recommended as part of a screening program for potential blood donors. The blood type of donors was determined in eight of the practices, whereas blood typing of recipients was not routinely performed. Ten of 25 practices performed blood crossmatches, but only one practice performed crossmatches in all cases. The distribution of direct costs per whole blood transfusion (500-ml unit) ranged from 25 to more than $300, with three fourths of the practices having costs less than $100. The higher-cost practices were those that maintained donors on the premises specifically for blood donation purposes.(ABSTRACT TRUNCATED AT 250 WORDS)