Background: Glutathione S-transferase (GST) enzymes that play a key role in detoxification of activated carcinogens are shown to be one of the potential modifiers of individualized risk for several cancer types. Objective: This purpose of this study was to investigate the frequency of the GSTT1 null genotype in Polycythaemia vera patients in sudan. Materials and Methods: Fifty polycythaemia vera patients and fifty controls were evaluated to determine the frequency of GSTT1 null genotype. Red cell parameters were performed by an automated cell analyzer. The GSTT1 null genotype was determined using polymerase chain reaction (PCR) method. Results: The GSTT1 null mutation was detected in 23% of cases (17% males and 5% females) and in 22% of control subjects. But the difference was not statistically significant (OR=1.2, 95% CI= 1.06-1.41, P= 0.64). Conclusion: We have observed that GSTT1 null genotype was similar among patients as well as control group and GSTT1 genotype was not related to laboratory findings in polycythaemia vera patients.