SUMMARYRegenerating protoplasts of the basidiomyceteSchizophyllum communewere labelled with radioactive N‐acetylglucosamine. The label was mainly incorporated in the alkali‐insoluble wall fractions R‐glucan (containing some hexosamine) and chitin. Light microscopic autoradiography showed a uniformly dispersed incorporation of label in primary cells and chain‐cells but emerged hyphae revealed a highly localized incorporation at the hyphal apex. Electron microscopic autoradiography showed that the label mainly appeared just outside the plasmalemma in the wall suggesting that chitin and R‐glucan are synthesized at the plasmalemma/cell wall