The effect of age on happiness, as defined by positive and negative affect, was examined in a survey of 2,727 persons of a broad age range (25-74) conducted by the MacArthur Foundation Research Network on Successful Midlife Development. The age-affect association was examined, controlling for a host of sociodemographic, personality, and contextual influences. Among women, age was related to positive affect nonlinearly but was unrelated to negative affect. Among men, age interacted with 2 key variables in predicting affect: extraversion and marital status. These findings lend support to recent life span theories of emotion and indicate that personality, contextual, and sociodemographic variables, as well as their interactions, are all needed to fully understand the age-affect relationship.