Abstract: It is necessary to study the "treatment schedule dependency" in the experimental chemotherapy of tumor for demonstrating the optimal dasage schedule and interval which is useful both for clinical trials and the understanding of the biochemical mechanism and cytokinetic characteristics of new agents. This paper reports our experimental results:1. Subcutaneously inoculated Ehrlich carcinoma (ESC) was suitable as a model of schedùle dependency tests. The results obtained from ESC were similar to those from routine experimental leukemia L₁₂₁₀ in three different schedules(i. e. single dose, intermitent pulse therapy once every four days for four times altogether and daily for fourteen consecutive days).2. The optimal schedule of several drugs was found to be as follows:Mecaphane: Intermitent therapy as well as daily course.Camptothecine: Intermittent therapy.Gyclophosphamide: Single dose.Vincristine: No schedule dependency.