The structure of carpusin, an extractive of the heartwood of Pterocarpus marsupium, has been established as 2-benzyl-2,4', 6-trihydroxy-4-methoxybenzo(b)furan-3(2H)one, on the basis of spectral evidence and its conversion to tetra-O-methylmaesousin and 4,6,4'-trimethoxyaurone.