Thirty-eight in-patients with endogenous- and 20 in-patients with non-endogenous depression, took part in a multi-centre 3-week double-blind trial where patients were randomly allocated to treatment with either 6 g L-tryptophan or 150 mg imipramine daily. Item analysis of Hamilton ratings, before the investigation and weekly during the trial period demonstrated few statistically different mean scores on individual items between the two treatment groups. After 3 weeks' treatment a statistically significant item mean reduction on the 0.1% level was found in the item Agitation in favour of imipramine-treated, and in the item Work and Activities in favour of L-tryptophan-treated endogenously depressed patients. After 3 weeks' treatment a statistically significant item mean reduction on the 5% level was found in the item Suicide in favour of imipramine-treated non-endogenously depressed patients. The present study has shown that, after 3 weeks' treatment, imipramine and L-tryptophan has decreased the mean score on individual items of HRS in about the same degree.