Concentrations of cadmium, copper, and zinc were determined in adults, larvae, larval faeces, and host plants of four monophagous and one oligophagous phytophagous insect species. In this way, transport of these metals from the plants via the larvae to the adults could be followed. The influence of metamorphosis on heavy metal concentrations was also studied. In general, metal concentrations tended to be lowest in plants, intermediate in larvae, and highest in adult insects. The exception was cadmium, concentrations of which were higher in larvae than in adult insects. Concentrations of cadmium were higher in faeces than in food plants, whereas no such difference was found for copper and zinc.