The change in absorptive, secretory, and motor functions of the gut can undermine human well-being. Appropriate motility along the gut plays a significant role in the absorption of nutrients and water across the gastrointestinal tract. Drugs can stimulate or reduce intestinal motility and thus alter the transit time of compounds across intestine and thereby hinder absorption. In vitro models are explained. Guinea pig ileum is explained. It is one of the most commonly used models to study the effect of drugs on gut motility, such as screening of drugs for spasmolytic activity. Other parts of the gut, such as duodenum and colon, can also be used as isolated preparations for gut motility studies. Cascade superfusion technique is explained. In vivo models are discussed. In vivo procedure was devised for determining the comparative potencies of spasmolytics against smooth muscle contractions induced by topically applied acetylcholine on rat colon, rectum, and urinary bladder. Colonic motility studies in rats are discussed. The anesthetized rat is used as one of the experimental models to study the influence of spasmolytic drugs on colon motility induced by carbachol. This model was used to study the stimulant property of an enkephalin analogue pentapeptide. Gut motility studies in dogs are described. This method includes the study of intraluminal pressure and motility of the small intestine in unanesthetized dogs with balloon catheter systems via duodenal Mann-Bollman fistula. Gut motility experiments are carried out in these animals after they have been fasted for 18 hours. For measurement of intraluminal pressure of intestines, air filled latex balloons attached to air filled polyethylene catheters are placed in intestine through the fistula and filled with air at a pressure of 10 mm of Hg. Recording is done on a polygraph after connecting the catheters to a pressure transducer.