The Coffin-Lowry syndrome (McKusick No. 30360) is a rare genetically transmitted disorder characterized by severe mental retardation, "coarse" facial appearance, thick soft skin, tapering fingers, and progressive skeletal abnormalities. X-linked inheritance is implied since the males are severely affected with variably mild manifestations in carrier women. We have performed a linkage analysis with many X-linked RFLP markers in 4 families. Positive two-point lod scores were obtained with DXS28 (z(theta) = 2.00 at theta = 0.05) and DXS41 (z(theta) = 1.26 at theta = 0.10). We performed a 5-point linkage analysis using the LINKMAP program assuming that DXS16 and DXS43 are a single locus and using the following fixed map (distances in centimorgans): DXS85 - 18cM - (DXS16, DXS43) - 13cM - DXS41 - 5cM -DXS28. This gave a multipoint lod score of 3.41 for a localisation in Xp22.2-p22.1, between DXS43 and DXS41.