Performance objectives are often neglected during the design phase of a project, and performance problems are often not discovered until the system is implemented. Therefore, there is a need from the industry to find a method to predict the performance of a system early in the design phase. One method that tries to solve this problem is the Software Performance Engineering (SPE) method. This report gives a short introduction to software performance and an overview of the SPE method for performance prediction. It also contains a case study where SPE is applied on an existing system.