The present invention concerns methods useful in treating one or more subtypes of irritable bowel syndrome (IBS), or useful in treating diarrhea. The invention relates to the use of peripherally selective kappa-opiate agonists, especially N-methyl-N-[(1S)-1-phenyl-2-((3S)-3-hydroxypyrrolidin-1-yl)ethyl]-2,2-diphenylacetamide and/or a pharmaceutically acceptable salt thereof for treating a subject having diarrhea-predominant IBS (IBS-D) or IBS with alternating diarrhea and constipation (IBS-A), or a subject having diarrhea.