A multi-centre, double-blind trial was carried out in general practice in 44 patients with symptoms of neurotic anxiety to compare the effects of treatment with either 400 mg chlormezanone at night or 5 mg diazepam 3-times daily for 4 weeks. The results indicated tht there were similar improvements in anxiety, duration and quality of sleep, and frequency of waking refreshed with both drugs. There was no significant difference in overall effectiveness of the treatments, as rated by both the patients and physicians. It is suggested, therefore, that chlormezanone could serve as a substitute for the benzodiazepine with the advantage of only once-daily dosage.