Family diet studies which measure total family consumption can determine only the average nutrient intake. A method has been devised to measure all family members' individual diets concurrently in order to learn how food and nutrient intake is distributed within the family. In this semi-weighed method, the total quantity of food available for consumption by the family is weighted at time of preparation or serving, and the distribution between family members is recorded in household measures. The method is described in detail. It provides data on individual consumption with an accuracy approaching that of a weighed survey. A co-operation rate of 73 per cent in a random sample of 74 households with two adults and two or three children indicates that this semi-weighed method can be used to assess family diets in a broad cross-section of socio-economic backgounds.