ABSTRACT Drawing from the Cognitive Affective Personality System (Mischel & Shoda, 1995, 1998), we argue for a need to examine within-individual variation in life satisfaction. Thus, employing a diary study of 76 fully employed, married adults we examined the magnitude, antecedents, and consequences of intra-individual variation in life satisfaction. Our findings establish a substantial amount of intra-individual variation, comparable to other personal evaluations assessed with a state approach (e.g., self-esteem), but less than that observed with major mood dimensions. In addition, concurrent changes in life satisfaction were systematically related to fluctuations in job and marital satisfaction; however, contrary to prediction, our results did not support a cross-level moderating role of Neuroticism in these associations. Our findings also lend support for the lagged influence of life satisfaction on next-day domain satisfaction ratings. Taken together, our findings demonstrate the systematic nature and importance of within-subject variation in life satisfaction.