The diagnostic approach of children with recurrent abdominal pain (RAP) was investigated by means of a standard protocol. The protocol consisted of recently developed laboratory techniques and 'routine' investigations. In addition, all patients were subjected to an extensive psychological investigation. The main results show that in a high percentage (42%) of patients organic abnormalities could be found. Particularly the small bowel seemed to be involved in the pathogenesis of the complaints. Furthermore, gastro-esophageal reflux appeared to be present in as many as 50% of the patients investigated and there might be a relationship with the abdominal pain complaints. Helicobacter pylori did not appear to play an important role in these patients. Comparing the results of the psychologic investigation with a pain-free control group, we did not find clear evidence that psychological factors play a role in the pathogenesis of these patients' complaints. Children with RAP, particularly when complaints exist longer than 6 months, need to be investigated for the presence of organic abnormalities that might provide an explanation for the complaints.