Radiography is an important diagnostic tool in guinea pigs and frequently requires sedation; however, neither inhalational nor injectable anesthesia (ie, benzodiazepines, α2 agonists, ketamine) have been shown to be optimal in terms of effectiveness, reliability, safety, and reversibility. This prospective study evaluated the use of intramuscular alfaxalone as a sedative for guinea pigs undergoing survey radiography. Thirty guinea pigs were administered alfaxalone (5 mg/kg IM), and physiologic variables were assessed. No respiratory depression or decreased temperatures were noted. Recoveries were uneventful. One disadvantage, however, was the lack of reversibility of effects, as no antagonist was available at the time of the study. Further studies are required to evaluate cardiovascular effects, use in unhealthy guinea pigs, and potential benefits of combining alfaxalone with other drugs for more invasive procedures.