The Wiskott-Aldrich syndrome (WAS) has previously been mapped to the proximal short arm of the X chromosome between the DXS14 and DXS7 loci. In this study, further segregation analysis has been performed using a newly identified WAS family as well as an additional marker probe, HOATL1. The results indicate close linkage between the WAS and OATL1 loci (Z = 6.08 at theta = 0.00) and localize the TIMP, OATL1, DXS255, and WAS loci distal to DXS146 and the OATL1 and WAS loci proximal to TIMP. These linkage data narrow the boundaries within which the WAS locus maps to the chromosomal region bracketed by TIMP and DXS146 and support the loci order Xpter-DXS7-TIMP-(OATL1, WAS, DXS255)-DXS146.