Plastic products may contain high levels of trace elements, which, upon final incineration, may affect the environment. In the case of packing material, may affect food quality. In this work, instrumental neutron activation analysis was applied to the determination of As, Ba, Br, Cd, Co, Cr, Fe, Sb, Sc, Se, Ti and Zn in plastic materials originated from household and hospital wastes. Toxic elements such as Cd and Sb were found at the levels of mg·kg–1 in some food containers and also high levels of Ti were found in opaque packages. The accuracy and the precision of results were also evaluated by interlaboratory comparison.