AbstractThe present study investigated possible relationships of metal levels and metal combinations to children's aggressive classroom behavior. Hair‐metal concentrations of lead, arsenic, mercury, cadmium, and aluminum were determined in 80 randomly selected elementary‐age children. Each child was also rated by his classroom teacher on the acting‐out subscale of the Walker Problem Behavior Identification Checklist. Parents of subjects were interviewed to control for confounding variables that may affect behavioral development. Regression data indicated that the set of metals was significantly related to increased scores on the acting‐out subscale (P<0.07) with lead being the major contributor (P<0.05), and the metal combinations were also significantly related to increased acting‐out scores (P<0.01) with the interaction of lead‐cadmium being the major contributor (P<0.001). A continuing reexamination of metal‐poisoning concentrations is needed, because metal levels and metal combinations previously thought harmless may be associated with aggressive class