Genetic and biomedical data from 346 cystic fibrosis patients of German origin have been evaluated. We demonstrated an age dependent distribution of CFTR genotypes, and confirmed the previously reported association between the dF508 mutation in the CFTR gene and pancreatic insufficiency. However 3 out of 22 pancreatic sufficient patients were dF508 homozygous. When patients were grouped with respect to height development, significant differences were seen in the distribution of J3.11-MspI alleles. We conclude that genetic determinants in and around the CFTR gene contribute to the variability in the clinical course of the disease.