The locus responsible for X-linked, nonsyndromic cleft palate and/or ankyloglossia (CPX) has previously been mapped to the proximal long arm of the human X chromosome between Xq21.31 and q21.33 in an Icelandic kindred. We have extended these studies by analyzing an additional 14 informative markers in the family as well as including several newly investigated family members. Recombination analysis indicates that the CPX locus is more proximal than previously thought, within the interval Xq21.1-q21.31. Two recombinants place DXYS1X as the distal flanking marker, while one recombinant defines DXS326 as the proximal flanking marker, an interval of less than 5 cM. Each of the flanking markers recombines with the CPX locus, giving 2-point lod scores of Zmax = 4.16 at theta = 0.08 (DXS326) and Zmax = 5.80 at theta = 0.06 (DXYS1X).