A double-blind, placebo-controlled, between-patient evaluation of the analgesic properties of oral meptazinol was carried out in 60 patients suffering from chronic pain due to rheumatoid arthritis and osteoarthritis. Patients were allocated, at random, to receive either 200 mg meptazinol every 3 to 6 hours as required or identical matching placebo for a total period of 72 hours. Data from 57 patients (30 on meptazinol, 27 on placebo) were suitable for analysis. Pain intensity in five major categories was assessed using a 4-point verbal rating scale by a clinician before the first dose and at the end of the trial period. Patients performed a self-assessment of pain prior to taking the first dose and subsequently at 2,4,24, 48 and 72 hours using 100 mm visual analogue scales and verbal rating scales. The clinician-rated pain scores showed no significant difference between the two groups in initial pain intensity. After 72-hours' treatment , there was a significant (p less than l.01) reduction in pain intensity after 2 hours which was maintained throughout the trial period. There was no significant reduction in pain intensity inpatients taking placebo. Visual analogue scale scores and pain intensity difference scores showed significantly (p less than 0.01) greater reduction in pain intensity at all time points in the meptazinol- treated patients.(ABSTRACT TRUNCATED AT 250 WORDS)