Background: Deletion types of genetic variants of glutathione S-transferase (GST) M1 and T1, the GSTM1 nulland GSTT1 null which are risk factors for certain cancers, have been ubiquitously found in human populationsbut their worldwide distribution pattern is unclear. Materials and Methods: To perform a meta-analysis, asystematic search for the literature on GSTM1 and GSTT1 null genotypes was done to identify 63 reports for 81human populations. Relationships between the GSTM1 and GSTT1 null genotype frequencies and the absolutelatitude of 81 populations were tested by Spearman’s rank correlation coefficient. Results: A significant positivecorrelation was detected between the GSTM1 null genotype frequency and the absolute latitude (r=0.28, p-value<0.05), whereas the GSTT1 null genotype frequency and absolute latitude showed a significant negative correlation(r= -0.41 p-value <0.01). There was no correlation between the frequencies of GSTM1 and GSTT1 null genotypein each population (r= -0.029, p-value=0.80). Conclusions: Latitudinal clines of the distribution of the GSTM1and GSTT1 null genotypes may be attributed to the result of gene-environmental adaptation. No functionalcompensation between GSTM1 and GSTT1 was suggested by the lack of correlation between the null frequenciesfor GSTM1 and GSTT1.