Sjogren-Larsson syndrome (SLS) is an inherited neurocutaneous disorder characterized by ichthyosis, mental retardation, spasticity, and deficient activity of fatty aldehyde dehydrogenase (FALDH). We identified a frequent FALDH mutation in exon 9 among SLS probands of European descent. This mutation is a 2-bp deletion of nucleotides GA 1297-1298 and results in premature termination of translation at codon 435 along with substitution of Arg and Cys for Glu433 and Gly434, respectively. The GA del1297-8 mutation was found in 10 of 21 European SLS probands and could be readily detected using an allele-specific PCR method. This GA deletion mutation or a previously identified common point mutation (C943T) was present in 66% of the European SLS probands, and the two mutations together accounted for 48% of the SLS alleles. Screening European patients for these two common mutations should be useful for DNA-based diagnosis of SLS and genetic counseling.