Korean Inst. of Inf. Sci. and Eng. (SIGPL and Softw. Eng. Soc.); Korea University; Korea Advanced Institute of Science and Technology (KAIST); KAIST, Software Process Improvement Center; KAIST, Defense Software Research CenterWe propose a tableau algorithm to decide bisimilarity of guarded normed and unnormed BPA processes, which is very intuitive and direct. It also has the advantage of helping us to show that the equational theory proposed by Huttel and Stirlin