Glutathione S-transferase M-1 (GSTM(1)) is an important family of phase II isoenzymes involved in inactivation of procarcinogens, which are factors that contribute to cancer genesis and progression. Null status of GSTM(1) is associated with decreased enzyme activity, and it has been widely studied as risk factor in bladder cancer (BC) susceptibility. However, the GSTM(1) null variant and BC form unclear association. We carried out meta-analysis to clarify the influence of GSTM(1) deficiency on BC. We estimated the pooled odds ratio (OR) with its 95% confidence interval (CI) to assess the association of the two conditions. Fifty studies with a total of 12,527 cases and 16,275 controls were included into the meta-analysis, which was not confined to a specific population. Overall, our meta-analysis supports the hypothesis that the GSTM(1) null variant is a determinant of BC susceptibility (OR=1.41 [1.30, 1.52], P<0.00001). The same patterns were observed in Caucasians (OR=1.38 [1.23, 1.55], P<0.00001), Africans (OR=1.68 [1.04, 2.71], P=0.03) and Asians (OR=1.46 [1.33, 1.61], P<0.00001). Furthermore, positive associations were also observed in both hospital-based (OR=1.48 [1.35, 1.61], P<0.00001) and population-based (OR=1.26 [1.10, 1.43], P=0.0006) studies. When data were stratified based on smoking status, we noted that smoking modified the association between GSTM(1) deficiency and BC risk (OR=1.41 [1.20, 1.65], P<0.0001) in smokers. However, no association was observed in non-smoking populations. In conclusion, this meta-analysis suggests that GSTM(1) null variant is a risk factor of BC.