This paper describes a rapid and reproducible technique for measuring the contractile activity of the colon, from strain-gauge signals, using a microcomputer data-processing PDS M 6800. This system can be used on-line, or after a 32 times compression, with only slight modifications of the data collection program. The motility index of the colon, calculated from the surface of the contractile waves, was automatically given at 5-min intervals. A series of comparative measurements of colonic motility and its changes after administration of drugs, such as morphinomimetics and spasmolytics, have been reported.