We identified 100% of the CFTR gene mutations, including three novel mutations, in 126 unrelated cystic fibrosis chromosomes from Tyrol, Austria. The frequency of the major mutation deltaF508 (74.6%) was not significantly different in Tyrolian CF-patients than in patients from Bavaria (71.0%) and Middle- and Northern Germany (71.9%), but was significantly higher than in patients from Styria (58.1%) or Northern Italy (47.6%). Interestingly, the distribution of the next most frequent mutations, R1162X (8.7%) 2183AA-->G, 2789+5G-->A and G542X (2.4% each), was more similar to the distribution of these mutations among CF-patients from Northern Italy than to those from Styria, Bavaria or Middle- and Northern Germany. Nine further mutations occurred once or twice. One of these, the missense mutation M1101K, is rare worldwide but very frequent in the Hutterite brethren, a small founder population which came from Southern Austria to Northern America. Three other different mutations (deltaL453, 1874insT and 4108delT) were present in single Tyrolian families and have not been described before. The identification of 100% of CFTR gene mutations in a particular CF population demonstrates the power of genetic analysis for the diagnosis and counselling of CF families in this restricted geographical area of Austria. Our study provides evidence for a closer genetic relation between CF patients from Tyrol and those from Bavaria or Middle- and Northern Germany as well as Northern Italy, than between CF patients from the two Austrian states Tyrol and Styria.