Investigations were made to determine the toxicity and the effect of 6 alkaloids (heliotrine, viridiflorin. platyphillin, seneciphilline, lasiocarpine and heliosupine) on the growth of subcutaneously inoculated hepatoma of mice and Ehrlich's adenocarcinoma. The greatest inhibitory effect on the growth of the hepatoma was shown by lasiocarpine. A considerable inhibitory effect on Ehrlich's tumors was also exerted by heliosupine.