When determining the cause of poisoning by antidepressant drugs, the data of laboratory toxicological studies of biofluids for the presence of this group of drugs are of key importance. Aim. To develop the methods for determining the antidepressant drug trazodone in the blood and urine samples using high-performance liquid chromatography with a UV spectrophotometric detection, which is suitable for analytical diagnosis of the thymoleptics intoxications. Materials and methods. The model samples of human biofluids spiked with trazodone were studied. The antidepressant was isolated from the blood and urine by the liquid-liquid extraction with methylene chloride from the alkaline medium at pH 9. Concomitant endogenous impurities were removed by extraction with diethyl ether from the acidic medium at pH 1. In the study of the blood the erythrocyte mass was pre-precipitated with the help of 10 % of trichloroacetic acid solution. Chromatographic analysis was performed on a microcolumn chromatograph using a column with a reversed-phase of C18. Results. The absolute retention time of trazodone in extracts from the model samples of biofluids was 17.91±0.09 min. The quantitative content of trazodone was determined at 250 nm by the calibration dependence of the chromatographic peak area on the concentration (μg/ml) y=(1.74∙10-3±1∙10-5)x. Under the indicated extraction conditions, 35±4 % and 78±4 % of trazodone were isolated from the blood and urine, respectively. Conclusions. The methods of trazodone isolation from the biofliuds by liquid extraction followed by the determination of the drug by high performance liquid chromatography with a multiwave UV spectrophotometric detection have been developed. The methods are recommended for using in the practice of forensic and clinical toxicology.