Genetic linkage has been analyzed between cystic fibrosis (CF) and a number of markers on the long arm of chromosome 7, including D7S15, COL1A2, PON, MET, D7S8, and TCRB, using a cohort of 47 Canadian and 13 Danish CF families. The analysis confirms the previous observations that both MET and D7S8 are closely linked to CF. Based on the result from one family, MET appears to be more proximal to the centromere than CF. Our analysis also suggests that genetic heterogeneity may account for the high recombination fraction between CF and D7S8 observed in another family. In addition, a strong linkage disequilibrium has been observed between CF and the two closely flanking markers.