Cystic fibrosis (CF) is an inherited multi-system disorder, characterized mainly by obstruction and infection of airways and by maldigestion and its consequences [1,2]. CF is the major cause of severe chronic lung disease in children and is responsible for most exocrine pancreatic insufficiency during early life. It is also responsible for many cases of salt depletion, nasal polyposis, pansinusitis, rectal prolapse, pancreatitis, cholelitiasis and insulin dependent hyperglycemia. CF may present as cirrhosis or other form of hepatic dysfunction, as well as congenital absence of vas deferens [3]. The estimated incidence is approximately one in 2500 [4]. The CF transmembrane regulator (CFTR) gene was identified and characterized in 1989 [5-7]; it spans approximately 250 kb at chromosome 7 (7q31.3), and consists of 27 exons that encode a membrane protein of 1480 amino acids. The CFTR protein functions as a cAMP-regulator chloride channel in exocrine epithelia [6-7]. Since the identification of the CFTR gene, more than 950 mutations and a large number of polymorphisms have been reported (<http://www.genet.sickkids.on.ca/cftr>). The DF508 anomaly is the most common CF mutation in all populations, with a mean worldwide distribution of 66.8% [8]. Only four other CF mutations (G542X, G551D, N1303K and W1282X) have relative world frequencies higher than 1%. Some CF mutations reach relatively high frequencies in certain geographic regions, such as R117H in northwestern Europe and R553X in central Europe, while others are only common in small regions, such as 621+1G®T in Central Greece; R347P and 1677delTA in south Bulgaria, G85E in south Greece and R347H in Turkey [8]. The molecular characterization of CF in the Republic of Macedonia was initiated in 1989 and the data on the molecular basis of CF in our country were published in 1990 [9] and again in 1998 [10]. Here we present updated and extended data on the frequency and distribution of CF mutations detected in a cohort of 121 patients from the Republic of Macedonia.