Clinical studies indicate that amisulpride – the second generation antipsychotic – does not cause any increase in plasma lipid peroxidation. We do not know in what way this medicinal drug affects the activity of the key enzymes of antioxidative protection and low-molecular antioxidants, including the plasma thiol groups. The study was aimed at establishing the effects of amisulpride, in doses recommended for treatment of acute episode of schizophrenia, on free thiols in human plasma under in vitro conditions and lipid peroxidation measured by the level of TBARS. Material and methods: Blood for the study was collected from 10 healthy male volunteers (aged 24-26 years) for ACD solution. Active substance of amisulpride was dissolved in 0.01% dimethyl sulfoxide to the final concentrations (278 ng/ml and 578 ng/ml) and incubated with plasma for 24 hours at 37°C. Control samples were performed for each experiment. The free thiols level was measured using the Ellman method, whereas the levels of thiobarbituric acid-reactive substances by spectrophotometric method (acc. to Rice-Evans, 1991). The results were analysed using the paired Student t-test (StatSoft Inc., Statistica v. 6.0). Results: Amisulpride after 24 hours’ incubation with plasma, as compared to control samples (without drug), caused an increase in the level of free thiols in plasma – statistically significant for concentration 578 ng/ml (p<0.03). At this concentration after 24 hours’ incubation with plasma the drug caused also a significant decrease in lipid peroxidation (p<0.003). Conclusions: Amisulpride in concentration 578 ng/ml, corresponding to doses used for treatment of acute episode of schizophrenia, induces antioxidative effects, causing a significant decrease in plasma lipid peroxidation and increasing the concentration of free thiols in plasma.