How can we enhance activation? Studying should be a challenging, yet rewarding activity for students who intend to graduate. The Flow theory (Csikszentmihalyi, 1990, 1997) predicts that differential levels of perceived challenge and skill (flow) are related to optimized mental states and increased activation. However, the influence of concurrent mental states and specific environmental cues for this state of optimal experience is unknown. In this study we explore the contextual and subjective determinants of flow in relation to activation in studying, and compare this with sports and watching TV or listening to the radio. Method: 43 undergraduate students at the University of Maastricht were assessed with the Experience Sampling Method for one week (Delespaul, 1995). At random moments 10 times each day subjects evaluated the social context, activities, and mood states. Analyses were done with multilevel random regression techniques. Results: We replicated the predicted flow-related patterns in activation and emotions. While overall activation was increased in high challenging moments ([beta] = 0.51; 95% CI: 0.36, 0.19), this effect was less pronounced during study ([beta] = -0.16; 95% CI: -0.25, -0.07). Skills levels did not affect activation ([beta] = -0.01; 95% CI: -0.06, 0.05). Concurrent emotions were independently and additionally related to activation ([delta][[chi square].sub.(4)] = 117.12, p is less than 0.0001). Unexpectedly, activation increased with demotivation ([beta] = -0.12; 95% CI: 0.16, 0.07). We found highly significant and additional effects of context for all the activities (study: [chi square] = 732.63; p is less than 0.0001; [R.sup.2] = 0.30; active leisure: [chi square] = 753.40; p is less than 0.0001; [R.sup.2] = 0.31; and passive leisure: [chi square] = 555.86; p is less than 0.0001; [R.sup.2] = 0.24). Conclusions. The Flow theory is a valuable model leading to predictions of optimal experience as well as activation. However, the dynamics of activity engagement are more complex and related to concurrent emotions and context. In the Dutch student culture, escaping boredom or compulsory duties seems to drive individuals more than pursuing flow.