Systemic lupus erythematosus (SLE) is a complex autoimmune disease in which genetic factors strongly influence susceptibility. Cytokines such as the interferon-gamma (IFNG) gene play a key role in controlling the immunity and inflammation, and therefore their polymorphisms may affect these genes' expression levels among individuals. We investigated the frequency of IFNG gene intron (+874) polymorphism, previously reported to be associated with IFNG production, in SLE patients compared to a control group. This population-based case-control study includes 154 SLE patients and 154 healthy control subjects with similar ethnic backgrounds. The genotyping was determined by polymerase chain reaction sequence-specific primer method and using the Chi-squared test for analyzing the association between this single-nucleotide polymorphism and SLE. The allele frequencies of the IFNG (+874) gene polymorphism were not significantly different between SLE patients and control subjects (72.7 vs 77%). However, there was a significant association between A dominance model of inheritance with arthritis (odds ratio = 7.64, 95% confidence interval = 1.56-41.64, P = 0.006, P(c) = 0.03). The result suggested that the +874 intron polymorphism of IFNG can be used as the marker for SLE susceptibility with arthritis in the Thai population.