There are often consistencies in the personal characteristics of associates used for particular purposes (e.g., people socialize with associates who are the same age, and ask advice of associates who are of the same religion). These consistencies are usually attributed to deliberate choices to use associates with certain characteristics; but the structured social contexts from which the associates are drawn may be more important determinants of associates' characteristics. Analysis of data from Fischer's Northern California Study indicates that: (1) associates serving certain purposes tend to be drawn from certain types of foci of activity (e.g., families, workplaces, neighborhoods, or voluntary organizations), (2) foci of activity tend to include people with particular characteristics (some are more homogeneous in age or in religion), and (3) these two factors together explain most of the tendency for people to use associates with certain characteristics for certain purposes.