The polymorphism of the Fc receptor for IgG class IIA (Fc gammaRIIA) in Vietnamese patients with systemic lupus erythematosus (SLE) was examined by using the polymerase chain reaction (PCR) method with genomic DNA and allele-specific primers. In the frequency of Fc gammaRIIA genotypes, the homozygosity of Fc gammaRIIA-H131 was four (8.3%) of 48 SLE patients and 16 (37.2%) of 43 healthy controls (P < 0.01). The allele frequency of Fc gammaRIIA-H131 in SLE patients was also significantly lower than that in the controls (P < 0.05). The unusual distribution of Fc gammaRIIA polymorphism suggested that Fc gammaRIIA might be involved in the development of SLE in Vietnamese patients.