GSTM1 deletion polymorphism was detected in 27/46 and 40/63 (58.7% vs. 63.5%, p = 0.567), GSTT1 deletion polymorphism in 8/46 and 14/63 (17.4% vs. 22.2%, p = 0.502), and a combination of GSTM1 and GSTT1 deletion polymorphisms in 6/46 and 8/63 (13% vs. 12.7%, p = 0.966) of our patients with JIA in whom stable clinical remission lasting for at least 6 months was achieved during MTX therapy and patients with JIA in whom stable clinical remission was not achieved during MTX treatment, respectively. This evidence concerns the gene GSTM1 and juvenile idiopathic arthritis.