Several groups have reported that abnormal phosphorylation of tau by Fyn, a protein-tyrosine kinase, may play a role in the neuropathogenesis of Alzheimer's disease (AD). In the present study, three common Japanese polymorphisms of the Fyn gene (-93A/G in the 5'-flanking region, IVS10+37T/C in intron 10 and Ex12+894T/G in the 3'-untranslated region) were studied in 127 healthy controls and 182 sporadic AD cases using a polymerase chain reaction restriction fragment length polymorphism method. A comparison of the allelic and genotypic frequencies of these polymorphisms between controls and sporadic AD cases failed to show any significant difference. These results suggest that the Fyn polymorphisms (-93A/G, IVS10+37T/C and Ex12+894T/G) investigated here have no genetic association with sporadic AD.