The Inventory of Family Feelings (IFF), a self-administered measure of interpersonal affect, maps a family's affective structure showing patterns of conflicted relationships and alliances. Three studies demonstrate that IFF scores have high reliability, construct and concurrent validity, and potential utility in family research. Families with identified patients and couples in marital therapy score less positively toward each other than control families, most of the negative affect in such families centers on and emanates from the identified patients, IFF scores are positively correlated with ratings of affect based on audio recordings of marital interaction and with Locke Wallace Short Marital Adjustment Test scores, and IFF scores and MMPI pathology indicies are negatively correlated.