Extensive ambient extraction of several metals from human hair compromises some assumptions concerning the binding of metals to hair and the biochemical process of metal incorporation into hair. Hair metal concentrations can reveal metal intoxications and metal deficiencies.The scalp hair selected for investigation included specimens of different colors from both sexes for various donor ages and from different geographic exposure areas. The hair samples were washed by agitation for 30 min with a 1% solution of sodium lauryl sulfate in a pH 7.2 buffer, rinsed repeatedly with deionized water, and oven-dried at 110 degrees C before 2-g portions were taken for extraction and digestion. Extraction involved agitation of the washed hair samples for 21 hr with 40 ml of 1% nitric acid at room temperature (23 degrees C). The extracted hair was digested in order to quantitate the amount of metal that was not extracted. Metal measurements were made by conventional flame atomic absorption spectroscopy. Potential interferences were investigated. Extraction varied between 82 and 100% for Na, Mg, K, Ca, Mn, Zn, Cd, and Pb. Removal of Fe, Ni, and Cu was 33-54%. Anatomical location, binding chemistry, biochemical incorporation, and mass screening are discussed.