Aims and objectives. During regional intraperitoneal chemotherapy cytostatics in prolonged dosage form, in particular, on the basis of various biodegradable hydrogels, such as dextran phosphate are applied. Aim of the study - a comparative evaluation of the antitumor activity ofcisplatin and cisplatin in prolonged dextran phosphate hydrogel form on Zajdel ascites hepatoma. Materials and methods. On 49 white no inbreed rats (n = 7) with implanted intraperitoneal Zajdel ascites hepatoma the antitumor activity of cisplatin in prolonged dextran phosphate hydrogel form with single intraperitoneal injection of the dosage from 3 to 8 mg/kg (≈ maximum tolerated dose, MTD) was evaluated in comparison with officinal cisplatin. The treatment efficacy was assessed by a statistically significant standard criteria: the absence of ascites by 32nd day of the experiment (complete remission) and an increase in life span of rats with ascites (T/C >_125 %, «treatment/control») in comparison with the rats without treatment (tumor growth control, where T/C = 100 %) or treated with officinal cisplatin. Macroscopic, pathomorphological and statistical analysis of the results were used. Results. It has been shown that hydrogel form of cisplatin compared to cisplatin was significantly more effective: complete remission 4/7-6/7 vs 0/7, T/C = 140-188 % vs 91-101 %, the volume of ascites 13,6 ± 6,6 ml vs 50,0 ± 7,9 ml (p = 0,004) because of a better tolerance. Regression analysis confirms that hydrogel form of cisplatin in used dose range significantly improves the rats survival with Zajdel ascites hepatoma, reducing the risk of death from tumor in 7-35 times and the relative risk with the dose of 5,5 mg/kg in 36 times (95 % CI3,86 + 327,60) (p = 0,002-0,005). Conclusions. The data obtained allow considering the hydrogel form of cisplatin as a promising prolonged this drug form of cisplatin by the intraperitoneal therapy and recommending it to preclinical study.