For patients undergoing carbamazepine treatment, measuring its concentration in serum and urine may be appropriate to guide treatment. Objective. To validate the developed technique for the quantitative determination of carbamazepine in blood serum and urine. Materials and methods. In the work, biological fluids (blood serum and urine) were used as research objects. Quantitative determination of carbamazepine was carried out in the concentration range from 0,50 to 50,0 mcg/ml on a high-performance liquid chromatograph with diode-matrix detection (Agilent Technologies 1200) by absolute calibration method. To assess linearity, calibration graphs were constructed and the concentrations of the model mixtures were recalculated. The correctness and precision of the developed methodology was determined on the basis of sample analysis data. Results of the study and their discussion. The calibration dependences for blood serum and urine in the range of carbamazepine concentrations of 0,5 – 50,0 mcg/ml are linear. Reverse recalculation of concentrations according to the calibration schedule showed that the deviations of carbamazepine concentrations from the actual values did not exceed 15%. The limit of quantification was 0,5 mcg/ml. At validation of the method, the calculated values of the relative standard deviation do not exceed 6%, relative error – 10,2%. Specificity of the method in relation to carbamazepine was confirmed by the absence of peaks interfering with the determination of chromatograms relative to «blank» samples. Conclusion. The obtained results showed that the method of determination is sensitive, accurate, provides analytical range of measurement from 0,5 to 50,0 mcg/ml with satisfactory expressiveness of work. The technique provides a practical solution for therapeutic monitoring of carbamazepine content, determination of its concentration in forensic chemical practice.