This report is based upon a pilot study of differences in social participation between sample populations in two Los Angeles areas, that is census tracts 35 and 63. The two tract populations are nearly identical with respect to two of the indices, social rank and segregation and differ on the third, urbanization. The field study included scheduled interviews on the participation of adult members of households in formal organizations, neighboring, cultural events, visiting, domestic activities, the mass media, the kin group, and other social structures. The low-urban sample differed sharply and consistently in the direction of more participation in the local community. The low-urban sample had a higher rate of membership and participation in formal organizations other than church, and, more important, a larger proportion of their organizations were local in nature. Furthermore, the members of formal organizations to which the low-urban sample belonged were more apt to live in the immediate local community. In the high-urban sample other members were most apt to be scattered over the metropolis as a whole.