Of the primary outcome measures the decrease in diarrhoea is the most difficult to catch. We have based our sample size calculation on the expected reduction in cases of diarrhoea (at the age of 3 months) over the last two weeks of one third from 12% to 8%. With a 95% confidence interval (alpha error 0.05) and power of 80%, an average number of infants of 35 per randomised community, and a coefficient of variation between the communities of 0.3, we will need to randomise 48 communities in each arm - a total of 96 communities. This will include 420 infants in each arm in each country, a total of 840 children per country and all in all 3360 children studied across the four sites. This sample size will very accurately give us the increase in EBF and be able to document the above decrease in diarrhoea morbidity.