A large number of toxic elements, including Th and U, in Scheldt and NBS river sediments, have been determined non-destructively by high energy photon activation. The length of irradiation varies between 1.5 hours for short lived-nuclides and 7–18 hours for long lived-nuclides. The induced activities are measured using a single open-ended coaxial Ge(Li) detector and the photopeak integrations are calculated using the total peak area method and the Cutipie computer program after substraction of the intrinsic background of the detector from each spectrum (Angela program). The photonuclear reactions and the best detection limits for 36 elements are indicated.