A prospective study was undertaken to evaluate the efficacy, safety, and patient acceptance of low-dose ketamine when used to diminish the pain of local anesthetic injections. The role of diazepam in preventing the untoward psychological effects of ketamine was also investigated. Our findings, derived from a postoperative questionnaire, reinforce the assertions of others, that ketamine is safe and effectively prevents pain in 85 percent of patients. While 13 percent of our patients hallucinated, most found the experience pleasant, and there were no "bad trips" or emergence reactions. Adequate premedication appears to be important in the successful use of ketamine. Whether sedation is augmented with diazepam or achieved with other medications does not appear to matter. A close supportive relationship with the surgeon and operating room personnel is probably as important as any pharmacologic manipulation in avoiding psychological mishap with low-dose ketamine.