The evolution and theories behind three popular service classification models (Customer Contact Model, Service Process Matrix, and Volume-Variety Model) are explored. In phase one of this research, a critical literature review reveals that the latter two models have ended up being quite similar to the well-known Product-Process Matrix in manufacturing. This first phase has also resulted in the formulation of six research inquiries related to these three models. In phase two, these research inquiries are addressed by analysing a set of empirically derived data. As a result, the Customer Contact Model is further developed. A number of questions are raised with regard to the validity of some of the theories behind the Service Process Matrix. Overall, the Volume-Variety Model is supported by the analysis. Finally, the question is answered whether it is better to use the manufacturing-based Product-Process Matrix, instead of the newly emerged models in service operations