Several multigenerational S-leut Hutterite families with cystic fibrosis (CF) were ascertained. Linkage studies with DNA marker loci MET and pJ3.11 (D7S8) were performed to determine whether (1) the CF gene in this inbred population is linked to DNA markers on chromosome 7, as it is in outbred populations of European origins, and (2) ancestral origin(s) of the CF gene could be determined. Our results indicate that the CF gene in Hutterite families segregates with chromosome 7 markers, identified by probes metH and pJ3.11. Thus, the CF mutation in Hutterites is likely to be either at the same locus as or at one closely linked to that reported in outbred populations. Heterozygous carriers could be distinguished from normal homozygous sibs of affected individuals. In the families studied, three different chromosome 7 haplotypes carried the CF mutation, raising the possibility that the CF gene may have been introduced into this population by as many as three different ancestors.