We reported earlier complete linkage between cystic fibrosis and an RFLP of the met proto-oncogene revealed by the probe pmetH. Another clone, pmetD, detects another polymorphism with the TaqI restriction enzyme. Further linkage studies, now involving 22 families, have confirmed the tight linkage of cystic fibrosis to the MET and D7S8 loci. Significant allelic association was found between CF and allelic series defined by the pmetH probe.