In a longitudinal study of child growth and nutritional status in Bangladesh, child morbidity was recorded using health interviews with the mother. The aim of the present study was to establish whether maternal reports of child illness were associated with the biochemical health status of the child. Children aged 2–5 years (n 117) took part in the study and their mothers were interviewed every fortnight by Bangladeshi fieldworkers. Maternal reports of diarrhoea were associated with significantly lower plasma albumin concentrations (P < 0·001), poorer intestinal permeability (P < 0·001), higher plasma immunoglobulin A levels (P < 0·005) and higher α-1-antichymotrypsin (ACT) levels (P < 0·05) compared with children reported to be healthy. Children with fever had significantly higher ACT (P < 0·001) and lower albumin (P < 0·05) levels compared with their healthy counterparts. Respiratory infections (RI) were not associated with any significant changes; however, reports of RI with fever were associated with significantly higher levels of ACT than either illness individually (interaction P < 0·05). These highly significant associations between maternal reports of illness and biochemical profiles of child health support the use of health interviews in developing countries.