This study was directed to an inquiry into a methodology for prioritizing and evaluating R & D alternatives for fuel cell technology, that can provide information for use in future decisions under the current uncertainty. A case study was performed for three cases of fuel cell development under the assumption that basic input data are same. The three cases are the case considering sequential R & D schedule only(Case 1), the case considering equivalent and excluding subprojects(Case 2), and the case allowing parallel efforts for each phase(Case 3). The following results were obtained; the probabilities of success for R & D phases in parallel projects are correlated, the probability of success for each project increases through Case 1, Case 2 and Case 3 successively and the expected dates of commercialization were notably shortened in Case 3.