In an open, clinical trial comprising a total of 21 depressed in-patients (6 men and 15 women) citalopram was administered in doses of 20-60 mg once daily for a period of at least 3 weeks. Fourteen of the patients were treated for 4 weeks, and 6 of these patients were treated for another 2 weeks. The CPRS subscale for depression (MADRS) and a global evaluation were used for assessment of the therapeutic effect. Twelve patients showed complete or partial response to treatment, and generally onset of therapeutic effect was seen within the first 2 weeks of treatment. Side-effects were generally few and mild, anxiety being the most frequent one. No pathological laboratory values were recorded, and apart from one case of slight and transient bradycardia no changes were observed in the cardiovascular parameters. Determination of plasma levels in 16 of the patients under presumed steady-state conditions showed an inter-individual variation between 28 and 616 nM/l for citalopram and between 32 and 338 nM/l for its monodemethylated metabolite for daily citalopram doses of 30-60 mg. The average ratio citalopram-desmethyl citalopram was 1.70. No correlation was found between clinical response and the plasma levels.