BACKGROUNDDelay phenomenon can be used for better blood supply of the flap in plastic surgery. Effects of Montelukast have been observed to reduce ischemia/reperfusion injury in various organs due to angiogenic and anti-oxidant effects. The present study aimed to determine the role of Montelukast as medical delay of the flaps.METHODSIn this experimental study, 42 Wistar rats were divided into 3 equal groups. These groups were Surgical Delay Group (SDG), Medical Delay Group (MDG) and Control Group (CG). In SDG, 8×3 cm rectangular randomized random skin flap was first surgically delayed at rats’ back. The MDG received 10 mg/kg oral Montelukast via orogastric tube for 5 days as medical delay. In MDG and SDG flap, harvesting was undertaken after a delayed period, but there was not any delayed period in CG. After delayed period, a segment of the skin flap was biopsied for assessing angiogenesis. After 14th days, the photos were taken and the size of the necrotic area of the flap was measured. RESULTSA significant difference was observed between the mean survival and angiogenesis (p=0.002). The same performance was reported between MDG and SDG, which were alike regarding survival and angiogenesis (p>0.05); while there was a significant difference between the control and surgical groups, as well as control and medical groups (p<0.05). Finally, the inflammation showed no significant difference (p>0.05).CONCLUSIONRegarding positive effects of Montelukast on survival and angiogenesis, it is recommended to be used as a medication for larger studies.