This study compared nitric oxide (NO) levels in 110 children with, and 110 children without, infectious gastroenteritis. Post-infection intestinal function was assessed in a subset. At least one pathogen was identified in 47.2% of cases. The most common diarrhoeal pathogens were rotavirus (22.7%) and norovirus genogroup II (11.8%). The levels of NO measured by median urinary nitrite:creatinine ratio were significantly higher in children with diarrhoea [23.6; interquartile range (IQR) 12.3-46.7] than without diarrhoea (7.8; IQR 4.1-13.2), P<0.001. The ratio was not significantly different between diarrhoeal cases with and without pathogens (P=0.148). Six of twelve children tested had intestinal dysfunction.