This article examines age differences in positive, but especially negative, interactions in close relationships. Two community-based representative samples of people from 13 to 96 years of age from the United States and Japan were used to explore these relationships. Analyses indicate stability across age in positive interactions but a general decline in negative interactions in both countries. Three possible explanations for this age difference in negative interactions were examined: social maturity, familiarity, and contact frequency. Results provide most support for the contact frequency explanation. And finally, intercorrelations across relationships, that is, spouse, mother, father, child, and same-gender best friend, indicate moderate to high intercorrelations across all ages with a slight increase among older Japanese age groups. These results can be summarized as lending support to a generalized reduction in negative interactions with age but exceptions are noted in specific relationships and cultural traditions.