This paper identifies and estimates the effects of several determinants on private investment in irrigation in Colombia. It attempts to quantify macroeconomic policy, environment, and violence variables that have been identified in previous studies as significantly affecting investment in agriculture in general, and in irrigation in particular. Variables such as violence, climate, and governmental price and credit policies are used to explain changes in private investment in irrigation across regions and over time. Violence negatively affects private investment. Climate affects the investment such that in regions with favorable climate conditions, investment in irrigation is less attractive, and appropriate government crop-price and credit policies promote investment in irrigation.