Lubiprostone, a bicyclic fatty acid chloride channel activator, is efficacious in treatment of chronic constipation and constipation-predominant irritable bowel syndrome. The study aim was to compare effects of lubiprostone and placebo on colonic sensory and motor functions in humans. In double-blind, randomized fashion, 60 healthy adults received three oral doses of placebo or 24 µg lubiprostone per day in a parallel-group, placebo-controlled trial. A barostat-manometry tube was placed in the left colon by flexible sigmoidoscopy and fluoroscopy. We measured treatment effects on colonic sensation and motility with validated methods, with the following endpoints: colonic compliance, fasting and postprandial tone and motility indices, pain thresholds, and sensory ratings to distensions. Among participants receiving lubiprostone or placebo, 26/30 and 28/30, respectively completed the study. There were no overall effects of lubiprostone on compliance, fasting tone, motility indices or sensation. However, there was a treatment by gender interaction effect for compliance (p=0.02), with lubiprostone inducing decreased fasting compliance in females (p=0.06) and an overall decreased colonic tone contraction after a standard meal relative to fasting tone (p=0.014), with greater effect in females (p<0.01). Numerical differences of first sensation and pain thresholds (p=0.11 in females) in the 2 groups were not significant. We concluded that oral lubiprostone 24 µg does not increase colonic motor function. The finding of decreased colonic compliance and decreased postprandial colonic tone in females suggest that motor effects are unlikely to cause accelerated colonic transit with lubiprostone, though they may facilitate laxation. Effects of lubiprostone on sensitivity deserve further study.