The effects of 3 different dosages of clotiazepam, a new short-acting thienodiazepine derivative, were evaluated by using psychometric ratings and EEG spectrum analysis. A random double-blind study versus placebo was performed on 8 patients affected by generalized anxiety disorder (DSM III). The effects of acute administration of clotiazepam 5 mg, 10 mg, 20 mg and placebo per os were evaluated by using HRSA and a time-signed semiquantitative scale for anxiety. The results of the trial confirm the effectiveness of clotiazepam in the treatment of anxiety symptoms, mainly in the reduction of peak anxiety levels, with dose-dependent characteristics. The modifications of the EEG parameters which resulted were dose-dependent and short-lasting with slight sedative findings.