AIM: This study was designed to investigate which biological agent, infliximab or tocilizumab, would more intensively keep suppressing oxidative stress among well-controlled patients as C-reactive protein (CRP) levels normalized in rheumatoid arthritis (RA). In addition, it was intended to clarify indicative factors of oxidative stress among well-controlled patients with RA. METHODS: We recruited 61 well-controlled (CRP < 0.3 mg/dL within normal ranges) patients with RA using biological agents (infliximab n = 33; tocilizumab n = 28), active RA patients with CRP > 1.0 mg/dL (n = 10) and healthy subjects (n = 10) and examined the fraction of oxidized albumin (oxidized-albumin [%]) as a marker of oxidative stress in addition to inflammatory measures and disease activity scores such as CRP, erythrocyte sedimentation rate (ESR), matrix metalloproteinase 3 (MMP-3), serum amyloid A (SAA), Clinical Disease Activity Index, Simplified Disease Activity Index, visual analog scale (VAS), Disease Activity Index of 28 joints (DAS28)-CRP, DAS28-ESR and renal function (creatinine clearance [CCr]). RESULTS: Oxidized-albumin (%) was significantly elevated among active RA patients (33.83 ± 5.31%) as compared with healthy subjects (23.00 ± 2.56%). Although oxidized-albumin (%) among well-controlled RA patients also increased, there was no difference with oxidized-albumin (%) between infliximab and tocilizumab groups (26.40 ± 5.44% in infliximab; 26.62 ± 4.53% in tocilizumab). In Pearson's correlation, oxidized-albumin (%) had significant correlations with CRP, MMP-3, ESR, SAA, age, CCr, VAS, DAS28-CRP and DAS28-ESR. With those variables, multiple stepwise forward regression analysis was conducted and revealed that CCr, DAS28-ESR and CRP are the statistically significant explanatory variables on oxidized-albumin (%) among well-controlled RA patients. CONCLUSIONS: We demonstrated that there was no difference with infliximab and tocilizumab on oxidative stress and we clarified that CCr, DAS28-ESR and CRP become indicative factors of oxidative stress among well-controlled RA patients.