Glutathione S-transferases (GSTs) enzymes are involved in the detoxification of several endogenous and exogenous substances. In this study, we evaluated the effects of two glutathione S-transferase polymorphisms, (GSTM1 and GSTT1) on bipolar disorder (BPD) risk susceptibility in a Tunisian population. These polymorphisms were analyzed in 229 healthy subjects and 109 patients with BPD, using a polymerase chain reaction. Statistical analysis was performed using SPSS 18.0. The relative associations between the GSTs genotypes and BPD were assessed by calculating odds ratios (ORs) and 95% confidence intervals (CLs). The study results demonstrated that individuals with GSTM1 [OR = 1.51, 95% CI: 0.93-2.45, p = 0.081] or GSTT1 [OR = 1.65, 95% CI: 0.95-2.88, p = 0.060] were not associated with the risk of BPD, whereas a significant association was found between individuals with both GSTM1/T1 null genotype and BPD risk [OR = 2.96, 95% CI (1.26-7.03), p = 0.005]. These genotyping finding revealed that the absence of both GSTM1 and GSTT1 activity could be a contributor factor for the development of BPD. (C) 2017 Elsevier B.V. All rights reserved.