This paper focuses on evaluation of serious games during the development of the game. Evaluation of serious games is a new and, according to the authors, a growing area of knowledge to address, which combines a number of disciplines. In the PRIME project funded by the European Commission, a serious game is under development. The paper presents the assessments done for developing an evaluation methodology for the PRIME game. The evaluation methodology developed for the PRIME game has limitations caused by the constraints for the PRIME project. Nevertheless, our experiences and the basis for the development of an evaluation methodology described in this paper will be useful for others who are developing or will develop serious games.