This study offers some empirical evidence on the relationship between population pressure and international conflict. Most of the work on population or in the area of environmental security focuses on internal conflict and does not include longitudinal and cross-national evidence to support its arguments. Here, we looked at the impact of population growth and density on international conflict involvement, initiation, and escalation for all states in the international system over the period 1930-89. Generally, population growth pressures had a significant impact on the likelihood that a state would become involved in military conflict. The relationship was modest, as expected, but seems to confirm the more pessimistic of the views of population and conflict. Significant military capability might be necessary for population pressures to lead to conflict, and low technology countries are more subject to population pressures and conflict involvement than their more advanced peers. In part, our results also suggest that some portion of the optimist argument may be correct -- advanced technology may mitigate some of the deleterious effects of high population growth. Although there was a positive relationship between population growth and conflict, there was little or no evidence that such growth made states more likely to be the initiator of that conflict or make that conflict more likely to escalate to war. Similar to earlier studies, we were unable to link population density to conflict at the nation-state level. There was scant evidence in all three analyses (involvement, initiation, and escalation) that overcrowding exercised any significant impact on state decision-making. It appears that states do not engage in conflict in order to acquire new land to support a burgeoning population. Thus, there are substantial limits to the validity of extending overcrowding arguments to the context of interstate relations.