The Leader Experience, Attribute, and Decision (LEAD) data set provides a rich source of new information about the personal lives and experiences of over 2,000 state leaders from 1875–2004. For the first time, we can combine insights from psychology and human development with large-n data on interstate conflict for a new theory of leadership and inter- state relations. The data set provides details about military experiences, childhood, education, personal and family life, and occupational history before leaders assumed power. The data is available in leader-year format and is compatible with existing tools for analysis such as EUGene (Bennett and Stam 2000). This research note discusses the motivation for the creation of the LEAD data set and discusses the coding decisions for most of the key variables. We provide a series of descriptive statistical illustrations of the data, and illustrate the depth of the available information with cases from Latin American leaders, showing the durability of these personal experiences across space and time.