[en] Continuing to the last report, the results of the basal study of therapeutic irradiation by ''Yayoi'' were reported as follows: The dose was measured in July, November, December, 1975 and April, June, 1976, and the calculation on one dimensional transportation was made in June, July, October, 1976. To obtain the most effective irradiation system for the patients under the circumstances of ''Yayoi'', the places to insert graphite and iron layers and polyethylene layer were improved, and the system to get better neutron flux was advocated. Using a human body type phantom, improvements of the human body permeability and of exposure to other than the affected part, etc, were discussed. (Kobatake, H.)