This open study evaluated the safety, tolerance and efficacy of multiple oral doses of butorphanol tartrate as long-term therapy for moderate to severe pain of various aetiologies. Twenty patients were given doses ranging from four to twelve 4 mg tablets per day for a period of 3 to 201 days (median 87 days). Median pain relief over the entire study was rated as good, very good or excellent in eleven patients (55%) and poor to fair in the remaining nine patients (45%). Global assessments were as follows: good to very good--twelve patients; poor to fair--eight patients. Ten of the twenty patients treated reported side-effects (sedation, light-headedness, dizziness, insomnia and headache) ranging from mild to severe. No drug-related abnormalities with respect to blood pressure, body-weight or laboratory data were evident.