This short course is the regular course on radial compressors thought at VKI to the turbomachinery students specializing in compressors in the context of the ‘Research Master in Fluid Dynamics’. It provides an overview of the present knowledge and flow models and intends to provide a good background for the people interested in the aerodynamic design of radial compressors. This 5 day course is now made available to a limited number of people from outside VKI.