In children with non-specific abdominal pain (NSAP) who were subsequently re-admitted to hospital with a further episode of pain within 30 days, the contribution of active observation to the initial and subsequent admission was evaluated and the diagnostic process reviewed. The cohort comprised all children with a discharge diagnosis of NSAP admitted to Royal Aberdeen Children's Hospital between January 1990 and December 1999. Data were extracted from a computerised database. A measure was made of the investigations employed in the children who were re-admitted and an arbitrary score produced in an attempt to measure the intensity and degree of the diagnostic process. This investigation score was then related to both clinical outcome and the need for revision of the original diagnosis of NSAP. A total of 1,238 children (675 males, 563 females) were admitted with NSAP; 46 (22 males and 24 females, age range 4-14 years) were re-admitted with further abdominal pain within a 30-day period. The total number of re-admission events was 53. In 19 children the subsequent diagnosis was revised. Ten of the 46 children underwent an operation; in 31 cases re-admission investigations were more detailed and invasive, but contributed to a change in diagnosis in only 13. There was no recorded mortality over the study period. In children re-admitted with abdominal pain, the subsequent diagnosis thus changed from the original in over one-third of cases. Most children undergo more invasive and more detailed investigations on re-admission in comparison to the initial episode of hospitalisation. The majority, however, continue to be managed conservatively. This study endorses the continued use of active observation in the management of NSAP in children, and recognises that even intense investigation may fail to contribute to a more specific diagnosis.