Mutation screening of the glucocerebrosidase gene by SSCP analysis revealed an abnormal pattern of exon 10 in two unrelated Italian Gaucher patients. Direct sequencing of the mutated samples identified a G6490-->A transition. The same mutation has been described before in a Japanese patient with Gaucher disease type III. The clinical phenotype of our patients was type I in one whose second allele carried the N370S mutation and type II in the other one with a L444P mutation. In this latter the G6490-->A substitution cancels a normal Msp I site, while on the opposite chromosome the T6433-->C mutation (L444P) introduces a new Msp I site. Thus, digestion with Msp I of the amplified exon 10 is a useful method for identifying the two mutations simultaneously.