Six new mutations have been identified in the CFTR gene. These mutations, representing three different categories—missense (R31L, W1098R), nonsense (E1104X), and frameshift (441delA, 681delC, 1461ins4)—are located in exons 2, 4, 5, 9, and 17b of the gene and presumed to cause cystic fibrosis (CF) in patients. All these mutations are probably rare in the population, as no additional examples were found for any of them in a cohort of 545 CF patients. Our study also revealed a benign sequence variation (3499 + 45T→C) in intron 17b. © 1995 Wiley-Liss, Inc.