This paper describes a methodology to design feasible interventions to improve weaning food hygiene practices of families living in extreme poverty. Educational messages to promote specific behavioural changes were defined and tested by utilizing a combination of ethnographic, survey and observational methods, and integrating viewpoints and suggestions of mothers and caretakers into the decision-making process. This new approach culminated in a household trial in which five groups, each of 15 non-practising mothers, were invited to adopt defined behaviours (handwashing before and after defined events, boiling water for reconstituting powdered milk, feeding gruel by spoon rather than bottlefeeding, not storing gruels and milks, and all four together). All initiated the advocated behaviours and most (53-80%) sustained the new behaviours and practised them every time during a one-month period. Of the four advocated behaviours, spoon-feeding was the most difficult to adopt wholly. The methodology was developed in response to the high priority given to reducing weaning food contamination for diarrhoeal disease control, and the lack of any existing methodology for defining appropriate educational interventions in resource-poor regions. This approach, with its combination of qualitative and quantitative methods and community focus, is recommended for future studies to design hygiene and other health education interventions in developing countries.