There is a tremendous amount of variation in conflict intensity both across and within civil conflicts. Some conflicts result in huge numbers of battle deaths, while others do not. Conflict intensity is also dynamic. Conflict intensity escalates, de-escalates, and persists. What explains this variation? We take one of the most prominent explanations for the onset and occurrence of civil conflict—variation in economic conditions—and apply it to the intensity and dynamics of civil conflict. Using an instrumental variables strategy and a rich set of empirical models, we find that the intensity of conflict is negatively related to per capita income. We also find that economic conditions affect conflict dynamics, as poorer countries are likely to experience longer and more intense spells of fighting after the onset of conflict.