Intra-party candidate selection processes are one of the prime mechanisms through which parties organize. This article seeks to examine empirically what factors account for variation in candidate selection processes. After identifying the key assertions developed in the literature, I use a unique cross-national dataset with data on the selection procedures of 512 parties in 46 countries to examine whether a party’s ideology, size, regime type, territorial organization and region affect the way parties select their legislative candidates. I pay special attention to the hypothesized relationships between electoral systems and selection processes, since the literature was indecisive and since research on the effects of institutions on legislators’ behaviour often amalgamated elections and selections. Underlying this amalgamation is an assumption that electoral systems determine candidate selection processes. I use my data to shed light on these relationships and provide a cautionary tale about amalgamating elections and selections.