Power modes in marital interactions were investigated in a laboratory observation study at the University of New Hampshire in 1975. Married couples (N=78) were the subjects in this study, whose focus was on the power modes (types of power assertion) used by the partners, shifting attention from the much-considered distribution of power in marriage to the question of how husbands and wives go about attempting to influence one another. A new system for coding marital interaction, the Marital Power Assertion Coding System (MPACS) was developed for this purpose, containing three broad divisions each with several sub-categories: (1) unqualified, direct power modes; (2) qualified, indirect power modes; and (3) bilateral power modes. Differences between the two groups in types of power assertions used were found to be generally consistent with findings in previous research on sex differences in communication as well as research efforts conducted after 1975. (Author/HLM)