Leukotrienes are important icosanoids group involved in a lot of normal and pathological states. Montelukast (MK) is a selective cysteinyl leukotriene receptor (Cys LT1) antagonist. Purpose. The purpose of the study is to observe the influence of MK on renal damage caused by experimental diabetes in rats. The experiment was carried out on four groups of adult male Wistar rats. Lot I was a witness and received 1.5ml of physiological saline ip. in unique dose on the first day of the experiment. Lots II and III have been caused experimental diabetes by streptozotocin (STZ) administration of 60mg/kg ip. in the unique dose. Lot III also received MK daily 10mg/kg/day daily 8weeks.Lot IV received only MK 10mg/kg/day daily 8 weeks. After eight weeks all animals were anesthetized and were sacrificed. The following pathological modifications were observed: tubular injury, glomerular hypertrophy and lesions, leukocytes infiltration. Obtained data showed that MK has significantly reduced the intensity of glomerular lesions (score 3.50+/-0.21 in STZ lot vs. 2.50+/-0.17 in STZ+MK lot p<0.01) and tubular damages. Renal interstitial leukocyte infiltration in animals with diabetes has been also reduced by MK. MK has a partially protective action against the lesions produced by experimental diabetes.