The clinical efficacy of fluvoxamine (DU 23000)--the first selective serotonin re-uptake inhibitor of the new class of 2-aminoethyloximethers of aralkylketones was investigated in endormorphous depressed patients during 5 weeks treatment with mean daily dosages of approximately 150 mg DU 23000. A marked and statistically significant improvement of the overall and detailed psychopathology was noted by means of the Global Clinical Impression and Hamilton Rating Scale as early as in the first week of drug administration. Bipolar patients tended to improve more than unipolar ones, retarded depressions more than agitated ones. An additional anxiolytic medication was occasionally required. The drug was well tolerated. Psychometric and laboratory findings did not show any significant changes. The findings are discussed in the light of the indolamine hypothesis of depression.