Communicated by Peter H. Byers Gaucher disease is particularly prevalent among Ashkenazi Jews; thus most studies have been reported on this ethnic group. We present the first data on Spanish patients with Gaucher disease and provide one of the first reports on a fairly well defined, large, non-Jewish population. Eight mutations were analyzed in 35 patients, with different clinical subtypes, by restriction enzyme digestion or allelespecific oligonucleotide (ASO) hybridization, after PCR amplification of genomic DNA. Analysis of the eight mutations allowed identification of 77.2% of the disease alleles, N370S and L444P alone accounting for 70%. Mutation N370S, carried by 31 alleles (44.3%), appeared to be the most prevalent in the Spanish population. The frequency of this mutation and of the N370SN370S genotype is closer to those described for Ashkenazi Jews than to the frequencies found in other non-Jewish populations. Mutation L444P, the second most abundant mutation, occurred in 25.7% of the disease alleles. Four alleles carrying mutation D409H (5.7%) were detected in patients of different clinical expression and one RecNciI allele in a type I patient. Mutations 84GG, IVS2 + 1, R463C, and RecTL were also screened but were not found in any of our patients. o 1995 Wiley-Liss, Inc.