A food stamp household is composed of all those who purchase food and prepare meals in common. All related co-residents must apply as a single food stamp household, no matter how they purchase and prepare food — except for elderly persons who are medically certified as unable to purchase and prepare meals separately. Other co-residents may apply separately if they purchase and prepare food separately, and residents in certain eligible institutional settings (e.g., shelters for battered women, residential drug treatment programs) may apply as separate households no matter how they purchase and prepare food.