In order to find the effect of genetic polymorphisms of GSTM1 and GSTT1 on blood pressure of individuals chronically exposed to sulfur compounds, the present study was done. Study subjects (38 males, 38 females) were residents of contaminated areas of Masjid-i-Sulaiman (southwest of Iran). The GSTM1 and GSTT1 genotypes were determined using a polymerase chain reaction (PCR)-based method. The non-parametric Sign test was applied in order to detect differences between the GSTs genotypes of study subjects and the normal mean values according to the sex and age of subjects. From four combination of genotypes, systolic blood pressure significantly decreased in combination of null-GSTM1 and present-GSTT1 (Z = -2.41; P = 0.016), and diastolic blood pressure significantly increased in combination of present-GSTM1 and null-GSTT1 (Z = +2.14; P = 0.032). It is speculated about polymorphisms of GSTs in individuals chronically exposed to natural sour gas, which contains H,S, fulfilling a physiological role(s) in regulating blood pressure. (C) 2004 Elsevier Inc. All rights reserved.