Thirty married couples were studied during naturalistic interactions to determine the extent to which variation in marital satisfaction could be accounted for by physiological and affective patterns between and within spouses. The authors hypothesized that (a) compared to nondistressed couples' interactions, distressed couples' interactions would show greater physiological interrelatedness or "linkage," more negative affect, and more reciprocity of negative affect and (b) these differences would be more pronounced when the interaction was high in conflict (discussing a marital problem) as opposed to low in conflict (discussing the events of the day). Heart rate, skin conductance, pulse transmission time, and somatic activity from both spouses were analyzed using bivariate time-series techniques to derive a measure of physiological linkage. Self-report affective data (obtained using a video-recall procedure) were analyzed using sequential analyses to derive a measure of affect reciprocity. The hypotheses were strongly supported; 60% of the variance in marital satisfaction was accounted for using measures of physiological linkage alone. Additional nonredundant variance was accounted for by the other physiological and affective measures.