This multicentre, double-blind, randomised trial in 109 patients compared the efficacy and tolerance of the novel selective serotonin and noradrenaline reuptake inhibitor (SNRI) antidepressant milnacipran (50 mg twice daily, n = 53) with the established tricyclic agent imipramine (75 mg twice daily, n = 56) over a period of 6 weeks, in patients with major depression (Montgomery -Angstromsberg depression rating score (MADRS) greater than or equal to 25). Initiation of antidepressant medication was conducted during a 2-week period of hospitalisation, after a 3- to 7-day washout period. Concomitant psychiatric medication was limited to lorazepam, cyamemazine, chloral hydrate and long-term uncomplicated lithium therapy. Assessment for efficacy using the MADRS and Hamilton rating scales of depression, a visual analogue scale and global evaluation revealed both agents to be highly effective (P = 0.0001) in this group of patients. Milnacipran was found to be of similar efficacy to imipramine. Tolerance, assessed by physiological and biochemical examinations with routine inventory and spontaneous report of adverse events, revealed a clear advantage for milnacipran. The incidence of anticholinergic events with milnacipran was about half that with imipramine and the overall incidence of adverse events by either reporting method was markedly lower with milnacipran than with imipramine. Furthermore, the patient drop-out rate with imipramine was double that experienced with milnacipran. Milnacipran appears to possess equal antidepressant efficacy to imipramine but with markedly superior tolerance. Therefore, milnacipran constitutes an important new treatment option in major depression. (C) 2002 Elsevier Science B.V. All rights reserved.