The study of party unity and its determinants is conceptually confusing, with terms such as ‘party discipline’ and ‘party cohesion’ used to denote both dependent and independent variables. Moreover, while the literature recognizes both anticipated sanctions and homogeneity of preferences as pathways to party unity, it ignores possibilities such as party loyalty and the division of labour within parliamentary parties. The article examines these different pathways to party unity on the basis of five waves of interviews with nearly all members of the Lower House of the Dutch parliament. The article finds least evidence for sanctions as a major determinant of party unity, with the possible exception of parties in the governing coalition. Homogeneity, loyalty and division of labour all seem to play an important role. Party unity might seem over determined, but the more likely explanation offered is that it is a case of ‘different horses for different courses’.