The overall objective of the X Chromosome Workshop is to gather together investigators from laboratories which are most active in the study of the human and mouse X chromosomes, in order to exchange mapping data, assemble-up-to-date working maps, and promote the sharing of materials. The 4th annual workshop will be held in St. Louis, Missouri, at the Ritz- Carlton Hotel on May 9-12, 1993. The workshop is by invitation only with an anticipated 80-85 participants. The 1994 X Chromosome Workshop will be held in Strasbourg, France.