This prospective nonrandomized trial was performed to evaluate the efficacy of salmon calcitonin (sCT) in controlling pain related to bone metastasis in cancer patients and the relation of sCT's analgesic efficacy with beta-endorphin blood levels. The study group consisted of 22 cancer patients with bone metastases (male 13 and female 9, age range 38-77 years). Pain control was first achieved by continuous subcutaneous (s.c.) morphine administration. The next increase in pain was managed with continuous s.c. administration of 400 IU/day sCT. Beta-endorphin blood levels were measured before and during sCT administration. The first measurement was taken before sCT administration; subsequent measurement occurred at 12, 24, and 48 hours and 7 days after the commencement of treatment. Pain scores were monitored by a visual analogue scale. A complete blood count and a biochemical screening profile were taken before the administration of calcitonin and also on the seventh and the fifteenth day of the administration. The results showed a satisfactory analgesic effect. The mean pain score before the calcitonin administration was 4.43 and the score on the seventh day was 1.17. The gradual reduction of pain score was associated with an increase in beta-endorphin blood levels (increase to 147.2% of baseline on the seventh treatment day). In three cases, no satisfactory analgesic effect was obtained and pain control was achieved by increasing the continuous s.c. morphine dosage. No significant side effects were observed. These data suggest that sCT in high doses may be a useful adjuvant analgesic when combined with low doses of morphine in continuous s.c. administration for the management of metastatic bone pain.