The study of interpersonal relationships in family groups (composed of three or more persons) gives rise to a number of theoretical and methodological problems not typically encountered in the study of dyads. In particular, the inclusion of a third (or more) member into the interactional domain presents complex issues which challenge the investigator's statistical-methodological expertise, theoretical-conceptual resources, and willingness and ability to incorporate perspectives from traditionally distant disciplines. This report focuses on two of the issues that are relevant to the study of family groups. The first of these is the relationship among measures, especially those concerned with determining the power structure within a family. The second issue addressed is that of second-order effects involving, as it were, relationship among relationships. (Author/SJL)