OBJECTIVE The prevalence of anaemia has been well studied particularly on etiology of nutritional anaemia in children of age group 5-10.9 yr in India. The present study was carried out to find out the prevalence and etiology of nutritional anaemia among 5 to 10.9 yr old corporation school children from urban slums. METHODS Urban Delhi slums were divided into four areas and one corporation school from each area was randomly selected. A total of 406 children from 4 each school were randomly selected over a period of one yr and prevalence of anaemia was estimated. Another subset of 95 anaemic children admitted to the hospital during the same period were evaluated for the etiology of nutritional anaemia. RESULTS Prevalence of anaemia as judged by WHO recommended cut-off values of haemoglobin among these children was 41.8 per cent. Pure or mixed iron deficiency anaemia was the commonest type of anaemia noted in 68.42 per cent (65 of 95) children followed by pure or mixed B12 deficiency noticed in 28.42 per cent (27 of 95) anaemic children. Of the pure variety, iron deficiency was the commonest cause occurring in 41.05 per cent (39 of 95) children. CONCLUSIONS Childhood anaemia continues to be a significant public health problem in school children aged 5 to 10.9 yr and iron deficiency either alone or in combination is the commonest nutritional cause of anaemia. Pure or mixed vitamin B12 deficiency is an important but yet not commonly recognized cause of anaemia among these children.