The present study was designed to determine the relationship between changes of plasma endothelin-1concentrations and development of colonic obstruction in sleep. Colons were bound in three sheep with sterilized plastic tubes to make pathological model of colonic obstruction. Samples were collected before and after modeling operation on both controls and models. Endothelin-1 concentrations were measured by radioimmunoassay. Plasma ET-11evels decreased continually after the modeling operation in the models,it dropped from a basal value of 60. 93±-18.66 to 34. 11±8.22 and 33. 54±11.12 pg/mL( P <0.05) on the 3rd and 5th day,respectively,which were also lower than controls 64. 16±12.93 pg/mL( P <0. 05). It suggests that colonic obstruction may induce a decrease in plasma endothelin-1 concentrations in sleep.