Colorectal hyperalgesia has been supposed to be one of the key pathophysiological roles in irritable bowel syndrome (IBS). Recent animal models have demonstrated that neonatal maternal deprivation (stress memory) or repetitive rectal distension (pain memory) in neonatal animal triggers long-term hypersensitivity to rectal distension, indicating that negative events including abuse or maternal separation in childhood may play a crucial role on development of IBS. Several molecules such as corticotropin-releasing factor, serotonin, nerve growth factor, myosin light chain kinase, chemical mediators from mast cell, substance P and calcitonin gene-related peptide released from transient receptor potential vanilloid receptor 1 (TRPV1)-positive primary afferent nerves have been proved to induce visceral hyperalgesia. Novel drugs based on these findings have been developed.