Although the contamination of hair with explosives can occur by means other than vapor interaction--e.g., direct contact with explosive particles or secondary contact through the direct transfer of explosive particles from hands to hair--vapor interaction was selected as the mode of exposure because this allowed the study to be performed without using human subjects. Cut hair tresses obtained from various sources were washed by repeated rinsing with sodium dodecylsulfate. The hair samples (Oriental, brown, blonde, and bleached) were strung vertically on an aluminum wire so they would stack into wide-mouth jars with a solid explosive at the bottom. The jars were stored in a fume hood in the laboratory, and the samples were incubated for various intervals. Following the exposure of the hairs to explosive vapor (TNT, RDX, PETN, TATP, and EGDN), the sorbed explosive was removed by extraction with acetonitrile and quantified. The sorption of explosives was significantly greater for the black hair than for the brown, blonde, or bleached hair. The rate of sorption was directly related to the vapor density. TATP, EGDN, and TNT remained on hair up to 2 days, and TNT remained up to 6 days. It is likely that similar persistence in air will be observed for PETN and RDX. Although explosive sorbed by hair was susceptible to removal during washing, laboratory washings indicated that some explosives persisted up to three rinses, i.e., TATP, EGDN, and PETN; and TNT remained after six rinses. 10 tables and 25 references