The Mikabu green rocks around Mt. Dohdaira in the northeastern Kanto mountains were studied stratigraphically and structurally. The green rocks are composed of volcanic formations of basaltic rocks, more than 1,000 m in thickness, accompanied by small amounts of sandstone, shale, and serpentinized peridotite. Their texture and mineral composition have been changed considerably by the Sanbagawa metamorphism of high-pressure type. The volcanic formations consist of gabbroic sheets, basaltic lava flows, and scoriaceous pyroclastic basalt in ascending order. The sequence of the formations would indicate the successive stages of development of a submarine volcano, which grew upwards and finally reached near the sea level. The volcanic formations are covered conformably by the Paleozoic sediments, and are exposed in the core part of an anticline of this region. The paleozoics are in high-angled fault contact with the volcanic rocks in places. No evidence of the thrust between the above two, which was pronosed bv HUZIMOTO (1937s). was found in this area.