A major problem in the adoption of advanced manufacturing systems such as F.M.S. (Flexible Manufacturing Systems) is the prerequisite economic justification process because of high investment needed for the acquisition and installation of F.M.S. While some of the benefits expected are readily quantifiable, others are very difficult or even impossible, using conventional method. Thus the investment in F.M.S. should be considered as a strategic decision rather than a tactical decision which concerns with only financial implications. In this paper we review papers on major justification techniques developed during thelast decade and identify the benefits of F.M.S. and describe the considerations in the justification of F.M.S. Also, we deal with the current and future research directions in justifying F.M.S.