The process of colonization has shaped the economic and demographic contours of the modern world. In this paper, we study the determinants of the occurrence and timing of colonization of non-European countries by Western European powers. Of particular interest is the role of early development measures that are known to be strong correlates of present-day levels of income. We show that non-European societies with longer histories of agriculture and statehood and higher levels of technology adoption in 1500 were less likely to be colonized, and tended to be colonized later if at all. We also find that proximity to the colonizing powers, disease environment, and latitude are significant predictors of the occurrence and timing of colonization, although their impacts are less robust to choice of country sample. Our models have high explanatory power, and their support for the significance of early development is robust to the use of alternative indicators of early development and disease, to the use of instruments to focus on the exogenous component of early development, and to the joint estimation of the colonization and timing equations to correct for potential selection bias.