This investigation was designed to shed light on household structure differences in mother - adolescent conflict. A total of 453 early, mid, and late adolescents from 3 ethnic groups completed questionnaires describing the rate and affective intensity of daily conflicts with mothers and fathers in single-mother (divorced or never married), 2-biological-parent, and blended (remarried) families. Compared to sons, daughters reported more disagreements with mothers and more negative affect in disagreements with mothers and fathers. Adolescents reported more total disagreements and more angry disagreements with single mothers than with mothers in 2-biological-parent families; adolescents in blended families fell in between. Reports of conflict with fathers did not differ across 2-biological-parent families and blended families. There were no household structure differences in conflict with parents (mothers and residential fathers combined), indicating that levels of conflict with single mothers are elevated by approximately the same number of disagreements that otherwise fall to fathers in 2-parent households. Potential moderators (adolescent age, ethnicity, and gender, maternal employment, prior marital status of single-mothers, socioeconomic status, and levels of social interaction) did not alter the results. For adolescents, single parenthood restricts the number of partners available for disagreement but has little bearing on the number or affective tenor of daily disagreements with mothers. In contrast, single parenthood is associated with elevated levels of family discord for mothers.