Börjeson-Forssman-Lehmann syndrome (BFLS) is a form of X-linked mental retardation (XLMR) with characteristic minor physical anomalies. It has no biochemical or cytogenetic markers. Heterozygous females may be entirely normal or may have mild-to-moderate manifestations. We studied 41 individuals from one family with BFLS for linkage on the X chromosome. The highest lod scores were 2.32 with DXS10 and 2.24 with DXS51, both at a theta = 0.0. A single recombinant was found between HPRT and BFLS. These results suggest that the BFLS locus is on the distal portion of Xq. Previously reported linkage studies in families with XLMR have not shown linkage with DXS10. This study suggests that one of the several X chromosome loci whose dysfunction is associated with mental retardation is located on distal Xq.