Cystic fibrosis (CF; MIM# 219700) is the most frequent recessive disease in Caucasian patients. However, immigration from the Middle East and Africa to Europe is revealing different CFTR mutations. Here, we have described an 875+1G-->A mutation, found for the first time in a homozygous state in an 8 yr old boy. He was the child of a couple of Egyptian first level cousins, both carriers of the mutation. The functional test revealed the 875+1G-->A to be a severe mutation, leading to defective protein function as detected by nasal potential difference (NPD) measurements.