The positioning of Expressed Sequence Tags (ESTs) constitutes an impor
tant step towards a functional map of the human genome, including cand
idate genes for human genetic disorders that have been localized by li
nkage analysis. We localized 59 ESTs on the human X chromosome, includ
ing 44 derived from infant brain and 15 from adult muscle cDNA librari
es. Localizations by a somatic cell hybrid panel were refined for five
cDNAs by mapping them in yeast artificial chromosome (YAC) contigs.