fa Morphometry Morphometry Original Original <strong>Purpose</strong>: The aim of this study was to evaluate the effects of HMT on protection of lung tissue exposed to HD in the rat. <strong>Materials and Methods</strong>: In this study twenty Albino Wister adult male rats weighting 200&plusmn;20 gram were used. Rats divided randomly into 4 groups (each group has 5 rats) as below: Normal saline group (NS), HMT group, HD group (0.25% HD) and HD+HMT group. Normal saline and HD solution were injected by intra tracheal catather. Animals in HMT and HD+HMT groups received HMT by intra peritoneal injection for 14 days daily. All rats were killed after 14 days, a part of lung tissue were removed, fixed and processed for histological evaluation by H&E staining and and apoptotic cell death study by TUNEL kit. In addition, biochemical study (catalase enzyme) was measured in all groups. <strong>Results</strong>: Histological examination and cell counting data revealed that there were no significant differences between Saline & HMT groups. Alveolar hemorrhage and inflammation, as well as, the number of apoptotic cells in the HD group was significantly increased when compared to HD+HMT group. <strong>Conclusion</strong>: HMT have prophylactic & therapeutics effects in the lung tissue against HD. Sulfur Mustard, Lung Tissue, Hexamethylenetetramine 0 0 http://anatomyjournal.ir/browse.php?a_code=A-10-304-212&slc_lang=fa&sid=1 Gholam Reza Kaka 10031947532846005111 10031947532846005111 No Seyyed Homayoun Sadraei 10031947532846005112 10031947532846005112 Yes Gholam Ali Mirshafiei 10031947532846005113 10031947532846005113 No Mahdi Saberi 10031947532846005114 10031947532846005114 No Mahvash Jafari 10031947532846005115 10031947532846005115 No