AIM: to evaluate and correlate the symptomatic, motor and sensory responses to two widely used categories of spasmolytic agents in irritable bowel syndrome (IBS). METHODS: 118 patients with IBS, diagnosed by Rome II criteria and 45 healthy individuals were studied. In the IBS subjects, pain severity, as well as the sensory response to rectal balloon distention and rectal and sigmoid motility, were studied at baseline and after two weeks therapy with either oral buscopan (20 mg three times a day, n=37), a buscopan suppository (30 mg once daily, n=21), oral drotaverine (80 mg three times a day, n=30), calcium gluconate tablets (one three times a day, n=16) as a control for oral agents, or calendula suppository (once daily, n=14) as a control for those who received a suppository. RESULTS: Buscopan, whether administered as a tablet or a suppository, produced a significant reduction in pain scores among IBS patients with predominant diarrhea. No significant differences were evident among other IBS subgroups or in response to drotaverine. None of the interventions had any effect on any of the parameters of rectal or sigmoid motility studied. However, both buscopan and drotaverine led to a significant augmentation of the rectal threshold for discomfort/pain among IBS subjects with predominant diarrhea [21.78 + or - 2.8 vs 39.60 + or - 2.4 (p<0.05), 20.5 + or - 2,8 vs 36.84 + or - 3.8 (p<0.05) and 22.18 + or - 2.8 vs 36.9 + or - 2.42 (p<0.05) for oral buscopan, rectal buscopan and oral drotaverine, respectively]. CONCLUSION: We conclude that the clinical benefits of supposed spasmolytic (anti-spasmodic) agents may relate more to effects on visceral sensation than motility.