We have used the lectins Arachis hypogaea (PNA), Canavalia ensiformis (Con A) and Triticum vulgaris (WGA) for the examination of bone forming cells in 8 variously differentiated cases of myositis ossificans. The development of myositis ossificans could be characterized with the appearance of a WGA binding cell population. In this cell population the lectin binding spots may be found in the perinuclear cytoplasm, possibly in the Golgi complex. The lectin binding of the bone forming cells has disappeared in the ripe myositis ossificans. We think that the WGA binding cell population may be equal with the progenitor cells, wandering in form the stroma ot the bone marrow and that the ability of WGA binding may be a characteristic developmental marker of these cells.