OBJECTIVE: To compare the estimated prevalence of malnutrition using the World Health Organization's (WHO) child growth standards versus the National Center for Health Statistics' (NCHS) growth reference, to examine the relationship between exclusive breastfeeding and malnutrition, and to determine the sensitivity and specificity of nutritional status indicators for predicting death during infancy. METHODS: A secondary analysis of data on 9424 mother-infant pairs in Ghana, India and Peru was conducted. Mothers and infants were enrolled in a trial of vitamin A supplementation during which the infants' weight, length and feeding practices were assessed regularly. Malnutrition indicators were determined using WHO and NCHS growth standards. FINDINGS: The prevalence of stunting, wasting and underweight in infants aged < 6 months was higher with WHO than NCHS standards. However, the prevalence of underweight in infants aged 6-12 months was much lower with WHO standards. The duration of exclusive breastfeeding was not associated with malnutrition in the first 6 months of life. In infants aged < 6 months, severe underweight at the first immunization visit as determined using WHO standards had the highest sensitivity (70.2%) and specificity (85.8%) for predicting mortality in India. No indicator was a good predictor in Ghana or Peru. In infants aged 6-12 months, underweight at 6 months had the highest sensitivity and specificity for predicting mortality in Ghana (37.0% and 82.2%, respectively) and Peru (33.3% and 97.9% respectively), while wasting was the best predictor in India (sensitivity: 54.6%; specificity: 85.5%). CONCLUSION: Malnutrition indicators determined using WHO standards were better predictors of mortality than those determined using NCHS standards. No association was found between breastfeeding duration and malnutrition at 6 months. Use of WHO child growth standards highlighted the importance of malnutrition in the first 6 months of life.