The nuclear resonance in the l6O(a, a)l6O elastic scattering reaction at 3.045 MeV has been used in concentration profilemeasurements ol oxygen in thin-film structuresThe concentration profile can be deduced lrom an energy scan ol the incoming a-particies, thus shifting the resonanceto different depths in the sample. The methocl has been applie<i to studies of the structures (a) an etched Si-surface, (b)Au evaporated on Si, and (c) a Au-Ge-Si structure. Eviclence is presented for the presence of oxygen in the Au layerand in the Ge layer.