What determines the subjective intensity of emotions? Four major groups of determinants are hypothesised: concerns (strength and relevance), appraisal, regulation, and individual differences. During six weeks subjects reported an emotion every week and answered questions on a computer. It appears that all four groups of supposed determinants are correlated with emotional intensity, the concern variables show the highest correlations. The importance of the determinants is not always the same, there are differences between the emotions and between the dimensions of emotional (...) intensity. The relation between regulation and emotional intensity is complex: Causal relations are expected in both directions. On the one hand, a more intense emotion requires more regulation (positive causal effect), and on the other, regulation will decrease the intensity (negative causal effect). Indications of the existence of both relations are found. Regulation and intensity are positively correlated. The canonical correlation of overall felt intensity and the regulation effort with the determinants is higher than the multiple correlation of only the overall felt intensity with the determinants. (shrink)