An Indiana family segregating a syndrome of X-linked mental retardation and skeletal anomalies was tested for linkage of the mutant gene to X-chromosome molecular markers. Lod scores of 3.27 and 3.06 (theta = 0) for the molecular probes St14-1 (DXS52) and Dx13 (DXS15), respectively, indicate that the disease gene is located in the terminal portion of Xq.