This research compares the relative impact of major life events, chronic stressors, and minor daily stressors on daily reports of mood. Analyses are based on daily diary data combined with interview data derived from a longitudinal study of 96 women sampled from the population of persons using the services of a neighborhood health center in Boston. The most important direct determinants of mood were found to be concurrent daily stressors and physical symptoms, and previous levels of psychological well-being. Life events and chronic stressors had indirect effects on mood through these other variables. The results serve to confirm and extend previous studies on the determinants of short-term changes in mood. The advantages and disadvantages of the temporal aggregation of time-series data are discussed.