Most paediatricians take great pleasure in making a diagnosis of infantile hypertrophic pyloric stenosis (IHPS; OMIM 179010). It is a most satisfying experience to observe the dramatic gastric peristalsis and to palpate the pyloric “tumour” during a positive test feed. Over 120 years after the condition has become a clinical entity,1 its aetiology remains unclear. The condition has an interesting age-specific and tissue-specific nature. IHPS is never seen beyond the age of 3 months except in reports of premature infants in whom enteral feeding had been started late. This suggests that a period of enteral feeding is required for the condition to become clinically evident. Either the defect is only critical to the infant in the first 3 months of life and/or there are compensatory mechanisms that will circumvent the pyloric obstruction over time. The main reported pathology is restricted to the pylorus associated with smooth muscle hypertrophy, and the pylorus has been shown to make a complete recovery after surgery.2 Recent advances in understanding of the control of gastrointestinal motility have provided a firmer basis for identification of the disease pathways underlying IHPS. The control and regulation of gastric motility and pyloric sphincter function is a complex system which involves the intrinsic myogenic activity of smooth muscle cells, the interstitial cells of Cajal (pacemaker cells), gastrointestinal hormones (eg, motilin, cholecystokinin and gastrin), the autonomic nervous system and the enteric nervous system. The excitatory pathway is mediated mainly by acetylcholine, tachykinins, serotonin, gastrin-releasing peptide and motilin. The inhibitory pathway includes the non-adrenergic, non-cholinergic enteric nervous system, the main neurotransmitters of which are nitric oxide and members of the vasoactive intestinal peptide family. Many of these pathways, …