The article analyzes the role of the reciprocity principle in the reproduction of social networks and the functioning of mutual assistance practices in local communities based on the results of authors’ empirical studies. Reciprocity is considered a principle of interpersonal and social relations, presupposing the existence of explicit and latent mutual obligations among their participants. Empirical diagnostics was centered on parameters of family-related, friendly, neighborly, professional networks of mutual aid as intensity and regularity of functioning, the focus of resource transfers, the nature of mutuality of obligations, motivation for the exchange of resources. The exchange of resources with parents and full-grown children is characterized by the highest degree of intensity. Most participants in such exchanges do not expect an equivalent volume of response services, and these interactions themselves have the character of generalized reciprocity. As we move toward «weak» ties (neighbors, colleagues, acquaintances), the attitude of balanced reciprocity dominates: receiving assistance, 50 to 57% of respondents expect an equivalent return. In the motivation of mutual aid, the attitude to a balanced reciprocity is most clearly expressed in professional and neighboring networks. In relations with friends, it is balanced by emotional-value and existential motives, which are dominant in family-related relationships. The normative significance of the principle of reciprocity and its system-forming character in various types of mutual aid networks is substantiated, and it has been proved that reciprocity in family ties has, first of all, an emotional-psychological and value background, in other networks of mutual aid the balanced nature of resource exchanges is a condition for their stable functioning.