This study is to explore whether there is presenilin 1 (PS1) gene mutation in Chinese familial Alzheimer's disease (FAD). There has been no such systemic research before in China. Using polymerase chain reaction, single strand conformation polymorphism (PCR-SSCP), followed by denaturing high performance liquid chromatograph (DHPLC) and DNA sequencing, we analyzed a Chinese family with early onset AD. The patients in this family showed a novel missense mutation in exon 4 of the PS1 gene (G to T change in codon 97), altering valine to leucine acid substitution. Because the change occurred in conserved domains of this gene, and is not present in normal controls, this novel mutation is likely to be causative of Chinese FAD.