The possibility of selection bias in the estimation of the effects of breastfeeding on subsequent survival is implied by the clinical evidence that children who are healthier at birth are more likely to be breastfed than their less healthy counterparts who may be prone to difficulties in sustaining breastfeeding. This paper addresses an important problem in understanding the association of breastfeeding and child survival with regard to reverse causation. It utilizes data on the reported reason for weaning to assess the degree to which reverse causality may be responsible for observed associations. The analysis indicates that children who are weaned in the neonatal period because of illness or weakness to suckle, experience a much higher risk of dying than others. This is not mainly because of the cessation of breastfeeding, but because of the original factor, being their illness. Any biases imparted by an initial selection mechanism appear, therefore, to have influence on the effectiveness of breastfeeding behavior.