Emphasizing that for any known toxic metal no safe dose level exists, this review describes existing evidence of the tetragenic effects of metal toxins on childhood development. Discussion of the currently available evidence of toxic effects focuses on cadmium, mercury, aluminum, arsenic, and, extensively, lead. The multicollinearity of metals is emphasized, and it is posited that metal interactions have a unique, negative, and synergistic relationship to children 's psychologic performance. The continuing lack of relevant and precise knowledge of the effects of low level exposure to toxic metals is noted.