Objectives. To evaluate the psychotropic specific spectrum activity of the novel peptide drug dilept and to find its effective doses in patients with schizotypal disorder. Material and methods. The effects of dilept were studied in 25 patients (33.4±10.0 years old) with schizotypal disorder (F21.3) with predominance of obsessive-compulsive, hypochondriac, phobic symptoms, mild cognitive impairment and negative symptoms. Patients were treated with dilept 60, 120 and 200 mg daily for 14 days as monotherapy (with allowance of phenazepam up to 2 mg single doses for insomnia and anxiety) followed by combined treatment with phenazepam in the case of insufficient effectiveness of dilept monotherapy. The Positive and Negative Syndrome scale (PANSS), Psychopathological Symptom Severity scale, Clinical Global Impression scale (CGI) and Wechsler Adult Intelligence scale (WAIS-R) were used as outcome measures. Results and conclusion. Dilept demonstrated the unique spectrum of psychotropic activity: antipsychotic with stimulating action, favorable effect on negative symptoms and cognitive dysfunction. Treatment action was the most evident when dilept was used in the dose 200 mg/day. There was no evidence of any side-effects known to be typical for antipsychotics. The efficacy of dilept and phenazepam combination is dependent on dilept’s antipsychotic and pro-cognitive effects, while benzodiazepine lacks these effects.