Non-steroidal anti-inflammatory drugs (NSAID) are increasingly popular in hospital medicine and general practice and are readily available over the counter. The vast majority of healthy children who ingest therapeutic doses of NSAID for a limited duration tolerate them without any significant adverse effects. However, the risk of renal toxicity is potentially increased in situations where there is stimulation of the renin-angiotensin system such as with volume depletion or in pre-existing chronic renal disease. We describe four cases which illustrate this complication occurring in a children's hospital. We have not proven cause and effect, but further research is needed to define the true risk of the potential renal complications of NSAID in patients at risk of dehydration.