This paper deals with how consumers arrange their ambulatory care in a system such as the United States which offers many possible choices. Patterns of the different affiliations (sources) that people maintain throughout the year for ambulatory care are formed. The data were obtained in interviews in a sample survey of Rhode Island households conducted in 1974. Although most people in the sample (89.5 per cent) cluster with one to three sources of care, there were over 80 people with four or more affiliations. For those persons with a large number of affiliations, the provider sets become quite varied. Two conceptual typologies are formed, one focusing on type (private physicians versus places) and the other focusing on both the speciality of the physicians involved and the number of different affiliations involved. The United States, at least in theory, maintains a 'free market' health care system. Are there limitations of choice imposed by differential distributions of knowledge, income or age? A wide array of social, demographic, and illness variables were examined to determine their relationship to the patterns.