We studied 17 pedigrees with 108 affected males with X-linked juvenile retinoschisis (RS; McKusick No. 31270) and have analyzed all of the known polymorphic markers in the RS region of Xp22.1-p22.2 between DXS987 and DXS41. By haplotype analyses we found 7 individuals who showed crossovers in this interval surrounding RS. We previously reported AFM291wf5 as the centromeric boundary, and this remains unchanged in the present study. A new recombination was identified on the telomeric side at (DXS1195, DXS418). Our data support the locus order Xpter – (DXS987, DXS207, DXS1053, DXS43) – (DXS1195, DXS418) – (RS, DXS257, DXS999) – (AFM291wf5, DXS443) – DXS 1052 – (DXS 1226, DXS274, DXS41) – Xcen; loci grouped in parentheses could not be mutually ordered by our genetic data. Physical mapping has indicated a distance of at most 900-1,000 kb between (DXS 1195, DXS418) and AFM291wf5. No recombination was observed between RS and DXS257 which lies in our new interval of interest, but one critical individual was not informative with this marker. Our data now define the smallest RS inclusion interval. This interval is contained on a single YAC from which we have identified expressed sequences as candidate