The experience sampling method is used to measure variance over time in events, moods, and behaviours in the work setting via palmtop computers in a sample of 41 employees. Theoretical propositions about event–mood–behaviour relations are derived from Affective Events Theory (Weiss & Cropanzano, 1996) and tested using within- and between-persons variance. The experiment found 56% of the variance in hedonic tone of mood was within- rather than between-persons. Hedonic tone was significantly related to both positive and negative work events in expected directions. The relationship between negative events and mood was approximately five times stronger than that between positive events and mood, even though positive events were reported three to five times more frequently than negative events. Hedonic tone was positively related to engaging in work withdrawal and negatively related to engaging in work tasks. Implications of these findings as well as the use of experience sampling for the study of dynamic workplace variables are discussed.