Chronic constipation is encountered frequently in clinical practice, and the use of laxatives is widespread in the general population. The need for effective and safe compounds stimulates research in the field. Unfortunately, to assess the colonic motility effects of these compounds, we have to rely on objective measurements available only through relatively invasive studies, such as manometric recordings of the motor activity of the large bowel. However, the possibility of studying almost the entire length of the viscus with these techniques allows a better definition of the pathophysiological processes involved in the genesis of constipation, and more insights into the effects of specifically acting drugs.