Backround. High-pressure liquid chromatography (HPLC) is the modern, advantageous and cost-effective analytical method. The validation process is essential in ensuring the quality of the analytical results, being necessary in the field of the pharmaceutical industry. Validation involves testing the method on different samples and comparing the results obtained with reference values, as well as evaluating other parameters, such as stability or detection limit. Thus, validation ensures that the results obtained are precise and specific. Mental illnesses have a great disabling power, a long evolution, and recovery requires considerable efforts and a long time. Thus, the research of new compounds used in the treatment of mental illnesses, as well as the development of their analysis methods, are very current. Dioxoindolinone, (1'-(2-oxo-propil)-spiro [[1,3] dioxolane-2',3'-indolin]-2'-one), is a new compound, derivative of isatin, synthesized in the Laboratory of Organic and Biopharmaceuticals Synthesis of the Institute of Chemistry. Aim of the study. Determination of some validation parameters for the HPLC method of Dioxoindolinone dosage. Material and methods. Dioxoindolinone, experimental synthesis series; Shimadzu LC-20AD liquid chromatograph with UV-detector SPD-20A, solvents and reagents in accordance with the requirements of the European Pharmacopoeia. Rezults. Linearity was investigated across concentration domains 5-30 μg/ml; the R² value constitutes 0,9984. Detection Limit (LOD) constitutes 1,27 μg/ml, Quantification Limit (LOQ) - 3,84 μg/ml. Conclusion. The HPLC method developed for Dioxoindolinone dosage shows specificity, linearity, accuracy, precision (repeatability).