Objective-To perform genetic sex typing during the Barcelona Olympic Games using polymerase chain reaction (PCR) amplification of Y chromosome specific sequences.Methods-The assay consisted of the amplification of a specific sequence corresponding to the repeat DYZI element from buccal smears samples of 2406 female competitors. Positive samples were reanalysed for the presence of another Y chromosome specific gene, SRY. Results-The expression of these two elements did not always correlate; six samples were found where the presence of DYZI but not SRY was detected. This presence of DYZI sequence in female athletes is higher than in unselected females, where no DYZ1 amplification was observed in any of the 1629 samples analysed. Conclusions-Amplification of DYZI repeat should not be used as the only index for determining genetic sex, at least in sporting events. (Br 7 Sports Med 1996;30:310-312)

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