We have used SIMS to measure the concentration profile of hydroxy-terminated polystyrene chains grafted onto a native-oxide-covered Si surface in deuterated polystyrene melts. The conformation of chains with only one labeled end was consistent with random-walk statistics near a reflecting wall and was independent of matrix molecular weight. The conformation of chains with labels at both ends underwent a loop-to-tail transition as the bulk volume firaction was increased. The grafting density increased with temperature and was inversely proportional to the molecular weight of the chains. © 1991 IOP Publishing Ltd.