Vitamin A deficiency is an important health problem globally including Bangladesh. The problem is greater among under-five children, particularly in malnourished. Vitamin A supplementation reduces morbidity from diarrhoeal diseases and also prevents future diarrhoea episodes. However, there are conflicting reports on the role of vitamin A supplementation on morbidity from acute lower respiratory infections (ALRI) including pneumonia. In non-malnourished children supplementation has been reported to be associated with increased incidence and morbidity of ALRI. The WHO committee[1] has reviewed both the risk and benefit of mega dose (200,000 IU) vitamin A supplementation during acute illness particularly diarrhoea, irrespective of the nutritional status of under-5 children and recommended vitamin A supplementation in areas where vitamin A status is low. In Bangladesh mega dose (200,000 IU) of vitamin A is routinely supplemented to under-5 children every 6 months. Absorption of vitamin A precursors from the GI tract is reduced in severely malnourished children, who are also lacking in retinol binding protein (RBP), required for transportation of retinol to target tissues. Thus it is established that a significant portion of the supplemented vitamin A is excreted in feces and urine of malnourished children. The excretion of vitamin A increases substantially during acute infections including diarrhoeal diseases. On the other hand, due to reduced RBP, concentration of free vitamin A increases in the body resulting in the possibility of adverse events including "pseudotumor cerebri". It has recently been observed that low-dose daily supplementation of vitamin A to malnourished children produces a better effect on recovery from acute illness and also in preventing infectious diseases among under-five children. However, the limitations of those studies included a small sample size, delayed assessment of retinol after supplementation among the others. Thus WHO felt that the issue needs to be addressed in a well-designed clinical trial. We hope that our proposed study will enable us to compare the efficacy of low-dose daily administration of vitamin A with that of initial mega dose followed by daily low dose of vitamin A in malnourished children presenting with acute diarrhoeal diseases with or without ALRI. If the results of this study indicate that the daily low-dose has similar efficacy to that of the currently recommended mega dose followed by daily low-dose of vitamin A, would have important programmatic implications.