The relations among different measures of interpersonal behavior and complementarity across level were examined in one session of a sample of therapy dyads (N = 26) and in an interaction between college students (N = 108). Four levels of complementarity, trait, aggregate situation, behavioral interchanges, and behavioral interchanges with base rates removed were examined as they covaried among themselves and with interaction evaluations. The four levels of complementarity were found to be fit by a simplex structure, and this structure was related to interaction evaluation in both samples. The complementarity-evaluation relation was mediated by base-rate-corrected complementarity. Implications relative to the operationalization of complementarity are discussed.