The present study compared the GSTT1and GSTM1 null genotypes among asthmatic patients with the levels of asthma severity whether mild (87.5% and 50% respectively), moderate (80.6% and 52.8% respectively) or severe persistent (94.1% and 47.1% respectively) and it revealed no statistical significance (P value: 0.236 and 0.892 respectively). This evidence concerns the gene GSTM1 and asthma.