This paper describes the use of computational fluid dynamics (CFD) as a tool to investigate fluid flow and heat transfer characteristics in louvered fin heat exchangers that are widely used in automotive industry. CFD supplies you with information from inside the heat exchanger like spatial distributions of temperature and velocity fields between the fins. The right interpretation of this information can reduce the number of prototypes and thus save time and money in the development process.Variations of grid density, differencing schemes and boundary conditions have been performed in 2D to ensure the reliability of the numerical results. With the recommendations of the 2-D study 3-D calculations have been made. The numerical results show good agreement with experimental data.The experimental values for overall pressure drop and heat transfer have been obtained using a test facility for heat exchangers at Behr. Distributions of local Nusselt numbers have been taken from investigations using the analogy between heat and mass transfer.