Gastrointestinal involvement occurs in approximately two thirds of children with Henoch-Schönlein Purpura (HSP) and usually is manifested by abdominal pain. Abdominal symptoms precede the typical purpuric rash of HSP in 14-36%; the symptoms may mimic an acute surgical abdomen and result in unnecessary laparotomy. Major complications of abdominal involvement develop in 4.6% (range 1.3-13.6%), of which intussusception is by far the most common. The intussusceptum is confined to the small bowel in 58%; its frequent inaccessibility to demonstration by contrast enema means that ultrasonography is the investigation of choice. Ultrasonography complements serial clinical assessment, clarifies the nature of the gastrointestinal involvement and reduces the likelihood of unnecessary surgery. Bowel ischaemia and infarction, intestinal perforation, fistula formation, late ileal stricture, acute appendicitis, massive upper gastrointestinal haemorrhage, pancreatitis, hydrops of the gallbladder and pseudomembranous colitis are seen infrequently. Earlier diagnosis and prompt treatment of intra-abdominal complications has reduced the mortality from 40% to almost zero.