Abstract: Pectins belonging to a group of substances termed dietary fibers were shown to have some anticancer properties. The main goal of this work was to estimate effects of low esterified pectin and calcium pectate on the Ehrlich ascites adenocarcinoma and Lewis lung carcinoma. Simultaneously the influence of polysaccharides on the efficiency of antitumor drug cyclophosphamide was assessed. Before the work the exact characteristic of the pectin samples was performed. Experiments were carried out in mice with tumor cells transplanted. The experimental mice were administered pectin preparations through gastric gavage for 7 days in experiment with Ehrlich ascites adenocarcinoma and for 9 days in experiment with Lewis lung carcinoma. Half of mice were also intramuscularily injected 150 mg kg-1 of cyclophoshamide. At the end of experiment animals were killed and the parameters of the tumor growth and metastasis were assessed. The results showed that calcium pectate in a dose dependent manner suppressed the growth of Ehrlich ascites tumor cells but did not affect the growth and metastasis of Lewis lung carcinoma. Low esterified pectin does not alter the growth of both tumors. At the same time, simultaneous administration of both pectin compounds and cyclophosphamide resulted in lowered growth rate of the tumors. The findings suggest that pectin compounds possess antitumor activity although different kinds of the polysaccharides do not exert similar effects on the different types of tumor cells. Also it was shown that pectins have a capacity to strengthen the efficiency of cyclophosphamide.