The patients evaluated in this study were classified into three groups of severe, moderate, and mild according to the severity of exposure to sulfur mustard. We evaluated the Immunological and Cytogenetical status of the patients after eight years of their exposure to sulfur mustard. The investigations revealed that the number of neutrophils, lymphocytes and monocytes in the patients with severe exposure were significantly different than in the normal population, while moderate and mild groups showed no significant differences. We also evaluated the DNA indices (hypo diploid, diploid & hyperploid) in the severe, moderate and mild groups comparing to normal population. The results indicate that in patients with severe exposure 22 out of 26 patients had aneuploidy, while moderate and mild groups showed no significant differences compared to the normal population. Regarding the numerical aberration rate and chromosomal breakage, our results indicated that there were no significant differences among moderate exposure, mild exposure and normal population.