High-dose intravenous immunoglobulins alter the disease activity of adult-onset Still's disease (AOSD). Because activation status of FcgammaR is possibly dependent on their genetic polymorphisms, we investigated whether the polymorphisms of FcgammaR IIa and IIIa are risk factors, and affect the clinical features of AOSD. Genomic DNA was extracted from 36 patients and from 197 healthy controls. Polymerase chain reaction for FcgammaR IIa and IIIa using the allele-specific primers and direct sequencing of FcgammaR IIIa polymorphic site were performed. The frequencies of FcgammaR IIa/IIIa genotype between patients with AOSD and controls were not different. The allelic frequencies of FcgammaR IIa/IIIa between patients with AOSD and controls were not different, either. However, the FcgammaR IIa-R/R131 genotype was associated with a higher concentration of hemoglobin (p=0.04) and stable liver function (p=0.009) than the other genotypes. The FcgammaR IIIa-F/F176 genotype was associated with significantly lower titers of serum ferritin (p=0.025), and higher serum albumin (p=0.037) and cholesterol (p=0.014) concentrations than the other genotypes. This study suggest that the FcgammaR IIa and IIIa polymorphisms might not be genetic risk factors for AOSD in Korean, but contribute to the activity of disease. FcgammaR IIa-R/R131 and IIIa-F/F176 genotypes, low-binding genotypes for IgG2a and G1, may have more protective effects in acute stage of the disease than the other genotypes.