It has been estimated that particles within the flow field of a 10-mm or mini-hydrocyclone experience local accelerations as high as 10 000 gravitation units. Although their operation is simple, the turbulent, swirling flow field within these devices offers a unique challenge to computational fluid dynamics (CFD). In addition to the computational challenge, very few experimental measurements have been reported in the literature on the flow field of the mini-hydrocycilone to which the CFD results may be compared. This research addresses the issue of predicting the separation efficiency of a volute entry 10-mm hydrocyclone. The feed flow rate is 4.5 litres/m (l/m) yielding a Reynolds number (based on the hydrocyclone diameter) of 9500 and a swirl number of 8.4. Using previously published flow simulation data, a multiphase system (consisting of a discrete oil phase and a continuous water phase) was analyzed for the purpose of obtaining separation information. These separation data were compared with laboratory separation experiments. Results indicate differences less than 20% for each droplet diameter. This information increased the level of confidence in the simulated flow field since there are no published velocity field data for the 10-mm hydrocyclone.