Flow injection-inductively coupled plasma mass spectrometry has been evaluated for determining the distribution profile of trace elements along a single strand of hair. Hair was cut into several mm long sections from follicle to the distal end. Each section was solubilized in a capped 1.5-mL polypropylene tube with small volume of nitric acid (typically 50 microL) at room temperature. After dilution an aliquot (50 microL) was introduced into the mass spectrometer by flow injection. The limit of determination was typically 5-50 pg with 5-10% precision (CV), depending on the element examined; this corresponds to sub-microgram/g concentrations of these elements in hair segments. Recent exposure and intake history of individuals to thallium or mercury could be reconstructed by this system.