A review of the current methods in modelling the performance of a hydrocyclone is presented in this paper. Hydrocyclones are an interesting and difficult unit of operation due to the complex physics that is occurring. The understanding of the main physical mechanisms, derived from experimental observations, enables development of analytical models to determine the optimum operating parameters for the highest hydrocyclone efficiency. Originating from first principles with some simplifying assumptions, the postulated analytical models are the introductory steps into improving the hydrocyclone design.  Recently, the application of computer simulations to model the flow patterns in a hydrocyclone are developed using both commercial and specialized computer programs. The applications of computational fluid dynamics algorithms have enormous potential in the design stages of a hydrocyclone. Although some technical difficulties still exist with computational models, it is now becoming feasible to consider various operating conditions and shapes of hydrocyclone in the design process. The combination of the different techniques could possible allow for an optimum hydrocyclone to be built for a specific type of application.