Sixty hospitalized subjects with chronic moderate to severe pain as a result of advanced cancer were enrolled in a randomized, parallel, double-blind trial comparing single doses and multiple doses of intramuscular dezocine (10 mg) with butorphanol (2 mg) and placebo. During the initial 6-hour efficacy evaluation, analgesia was measured using verbal and visual scriptors and vital signs, and acute toxicity information was recorded. Subjects with initial pain relief entered the 7-day multidose portion of the trial, and efficacy and toxicity data were recorded daily. After the initial dose the peak analgesia of the active agents was similar, but the duration of analgesia was longer with dezocine. After multiple doses, dezocine was superior to butorphanol in terms of length of treatment. Dezocine had less toxicity than had butorphanol after both single and repeated doses, further suggesting that dezocine may be beneficial in managing chronic cancer pain. The described study design is unique in that it compares the analgesic efficacy and toxicity of several analgesics with placebo after both single and multiple doses in the same subject. This method may prove to be an alternative pain model to evaluate chronic cancer pain.