Correlations between the concentrations of some heavy metals in scalp hair and in blood and/or urine have been reported. These reports clearly show exposure to these heavy metals, arsenic, lead and mercury, is reflected in elevated concentrations in the hair. In addition, these reports strongly indicate systemic intoxication with these heavy metals is not only reflected in elevated concentrations in the hair but in the blood and urine as well. Consequently, hair analysis has potential merit as a screening procedure for poisoning by there heavy metals. However, questions regarding the exogenous versus the endogenous deposition of heavy metals in the hair and uncertainties about the normal concentrations of heavy metals in the hair remain unresolved. Until these issues are resolved, hair analysis must remain as a screening tool that reflects exposure to toxic elements, and clinical signs and symptoms are needed to complete the diagnosis of heavy metal poisoning.