Hyoscine and drotaverine effectiveness was compared for the purposes of achieving optimum distension following insufflation in CT colonography. The in vitro effects of hyoscine and drotaverine on tone and contractility of SM preparations isolated from different areas of human colon were studied by isometric registration of contractile activity. Both medications have a relaxing effect on SM preparations and inhibit their spontaneous contractions. The drotaverine-induced effects were reliably more marked than the hyoscine-induced ones. CT colonography was performed in 70 patients who were injected with equal doses of either hyoscine (n=32) or drotaverine (n=38). The degree of drug-induced distension in both groups was determined by measuring the lumen of the colon on a 2D reconstruction. In most colon areas the width of the distended lumen was greater in the drotaverine-treated patients. We concluded that drotaverine can be used as a means to facilitate colonic distension.