The incidence of cystic fibrosis (CF) and the frequency of disease-causing 
mutations varies among different ethnic and geographic populations. The Jewish 
population around the world is comprised of two major ethnic groups; Ashkenazi 
and non-Ashkenazi. The latter is further classified according to country of 
origin. In this study, we analyzed the incidence of CF and the distribution of 
CF mutations in the general Jewish population in Israel and in most of the 
Jewish ethnic subgroups. The disease frequency varies considerably among the 
latter. Among Ashkenazi Jews, the frequency of CF is 1:3300, which is similar to 
the frequency in most Caucasian populations. Among non-Ashkenazi Jews, the 
disease occurs at a similar frequency among Jews from Libya (1:2700), Georgia 
(1:2700), Greece and Bulgaria (1:2400), but is rare in Jews from Yemen (1:8800), 
Morocco (1:15000), Iraq (1:32000), and Iran (1:39000). So far, only 12 mutations 
have been identified in Israeli Jews, and this enables the identification of 91% 
of the CF chromosomes in the entire Jewish CF population. However, in each 
Jewish ethnic group, the disease is caused by a different repertoire of 
mutations. The frequency of identified mutations is high in Ashkenazi Jews 
(95%), and in Jews originating from Tunisia (100%), Libya (91%), Turkey (90%), 
and Georgia (88%). However, a lower frequency of mutations can be identified in 
Moroccan (85%), Egyptian (50%), and Yemenite (0%) Jews. For genetic counseling 
of a Jewish individual, it is necessary to calculate the residual risk according 
to ethnic origin. Carrier screening of healthy Jewish individuals is currently 
feasible for Ashkenazi Tunisian, Libyan, Turkish, and Georgian Jews. These 
results provide the required information for genetic counseling of Jewish CF 
families and screening programs of Jewish populations worldwide.