The gas chromatography-mass spectrometry analysis of scalp hair segments found the presence of ecstasy in 19 of 21 subjects and amphetamine/methamphetamine in 8 subjects. Seven subjects had hair levels of the MDMA metabolite MDA in amounts equal to or greater than those of MDMA, suggesting the use of MDA in addition to MDMA. None of the subjects who tested positive for MDA or amphetamine/methamphetamine reported an awareness that they had been ingesting any drug other than ecstasy (MDMA). Results of analyses of some of the suspected ecstasy tablets submitted to Drug analysis Service of Health Canada in Toronto indicate that ecstasy tablets in Ontario can contain a variety of components, including MDA and methamphetamine, although 40 percent to 70 percent of analyzed ecstasy tablets have contained only MDMA. Further investigation should determine whether this is a phenomenon limited to Ontario, the relative harm to humans of MDA and methamphetamine compared with MDMA, and the explanation for the inclusion in ecstasy tablets of such drug combinations by clandestine laboratories. 5 tables, 2 figures, and 38 references