Reactive oxygen and nitrogen species are involved in the pathology of rheumatoid arthritis (RA). Polymorphisms in genes coding for superoxide dismutases (SOD2 and SOD3), catalase (CAT), tumor necrosis factor-alpha (TNFA) and inducible NO synthase (NOS2A) may influence RA activity. We determined SOD2 Ala-9Val, SOD3 Arg213Gly, CAT C-262T, TNFA G-308A, TNFA C-857T and NOS2A (CCTTT)n polymorphisms in 327 RA patients. Carriers of CAT -262T and TNFA -308A allele had lower mean disease activity score of 28 joint count (DAS28) values than patients with CAT -262CC and TNFA -308GG genotypes (p = 0.014 and p = 0.046, respectively). Patients with the combination of CAT -262T and TNFA -308A allele had lower mean DAS28 values and a higher probability for low disease activity than non-carriers (p = 0.003, OR = 3.585, 95% CI = 1.538–8.357). Our results suggest that CAT and TNFA polymorphisms alone and in combination influence the activity of RA.