A tree tonic, which was the powder composed of seven kinds of herb medicines, rice brain, soybean, rice, pearl barley and etc., was exploited and its effectiveness on recovering or maintaining the vitality of trees was examined by the field treatment at seven pine (Pinus densiflora and P. thunbergii) stands in Hiroshima and Yamaguchi Prefectures. The tonic solution was injected into the soil at 6-90 points just around each trunk of about 3,700 pine trees (treatment trees). One year later their vitality, which was evaluated by the leaf longevity and divided into eleven grades, was measured again as same as just before the treatment. The average mortality of the treatment trees was only 0.8(nil)er year, while 17.10f non-treatment, i. e., control 4,700 trees, which were adjacent to the treatment trees, died during the year. The vitality of treatment trees became up on an average rather more than before treatment. The facts suggest remarkable effects of the tonic on the vitality of trees.