The aim of the present study is to investigate the pharmacodynamic effects of Origanum majorana (Lamiaceae) on isolated smooth muscles preparations. Maximum re laxation of isolated guinea pig's ileum and rat's colon was achieved by addition of 50 μg of Origanum majorana /ml bath. While in isolated rabbit's duodenum, it was achieved by addition of 100 μg of Origanum majorana /ml bath. The effect of graded increased concentrations of Origanum majorana on isolated rat's uterine muscles was examined during various stages of sex cycle. Maximum relaxation of isola ted rat's uterine muscles was achieved by addition of 200 μg of Origanum majorana /ml bath. It was concluded that, Origanum majorana directly inhibits the smooth muscles of gastrointestinal tract and those of uterus. These findings indicated that Origanum majorana had a significant antispasmodic effects and might have some cl inical benefits for treatment of gastroint estinal disorders as colic.