Phospholipid metabolism in inflamed tissue of the mouse skin which had been induced by the application of 1-chloro-2, 4-dinitrobenzene (DNCB), croton oil, or irradiation of ultraviolet rays was examined, and it was found that phospholipid levels had increased in theinflamed tissues. In the case of ultraviolet rays, the increase was temporary, and the level returned to that of control after 3 or 4 days. In the case of DNCB or croton oil, the level increased after a decrease for a short period. The pattern of the increase between physical and chemical irritation was different. Increase of incorporation of 32-P into phospholipid in inflamed tissue was examined, and it was observed that the level reached a maximum after one day. It is thus assumed that phospholipid plays an important role in the mechanism of inflammation.