This placebo controlled, double-blind, cross-over trial involving 20 patients was conducted to assess the effect of ispaghula husk on the major bowel symptoms and the whole gut transit time in irritable bowel syndrome (IBS) and to determine if changes in these parameters were related to global improvement. All 20 patients were interviewed at the end of the treatment periods and 14 patients kept concurrent daily records. Ispaghula therapy resulted in improvement in global symptoms and satisfying bowel movements (P less than 0.001) but produced no change in abdominal pain or flatulence. There was a correlation between the improvement of well-being and the number of days of satisfying bowel movements (P less than 0.001) but not with the indexes of pain, stool frequency or changes in the transit time. The easing of bowel dissatisfaction appears to be a major reason for the therapeutic success of ispaghula in IBS.