Objective — the efficacy of sulpiride in patients with anxiety disorders depending on the serum serotonin concentrations was evaluated. Material and methods. We examined 132 patients with anxiety disorders. The higher levels of serotonin were foundin 81 (61.3%) of patients, normal levels in 24 (25.8%) and lower levels in 27 (20.5%). Sulpiride was used in doses from 50 to 400 mg. Average treatment duration was >90 days. Results. The positive effect of sulpiride monotherapy was identified in patients with higher and normal levels of serotonin. No clinical effect of sulpiride was noted in patients with lower serotonin concentrations. Conclusion. The efficacy of sulpiride depends on serumconcentrations of serotonin. It can be assumed that serotonin concentration is a marker of sulpiride treatment efficacy in patients with anxiety disorders.