This report describes the results of a survey of the nutritional health of Iban from 24 longhouse villages in Song and Kanowit Districts during February to April 1990. The principle findings are: 1. Kanowit District clinic records of child nutritional status may have significantly underestimated the prevalence of low weight-for-age. 2. The growth performance of children aged 2–9 y in Kanowit appears to be slower than that of children in Song. 3. A concentration of respiratory morbidity in Kanowit, affecting children and adults of all ages, significantly contributes to this pattern. 4. Kanowit men aged 18–40 are shorter in stature than those in Song. 5. There is evidence for chronic energy deficiency in adults aged over 45 y, with a prevalence probably exceeding 10% and rising with age, particularly in women. This is significantly influenced by morbidity independently of the ageing process. 6. Resting energy expenditure in men and women significantly exceeds that predicted by internationally recommended methods, and requires further study. 7. Further investigation is required to substantiate and explain marginal evidence that Kanowit men have greater physical capacity for work than men in Song, and elucidate the implications of variable physical fitness for household income from subsistence activities