To achieve a behavioral goal in a complex environment, such as problem-solving situations, we must plan multiple steps of action. On planning a series of actions, we anticipate future events that will occur as a result of each action, and mentally organize the temporal sequence of events. To investigate the involvement of the lateral prefrontal cortex (PFC) in such multistep planning, we examined neuronal activity in the PFC while monkeys performed a maze path-finding task. In this task, we set monkeys the job of capturing a goal in the maze by moving a cursor on the screen. Cursor movement was linked to movements of each wrist. To dissociate the outcomes of the intended action from the motor commands, we trained the monkeys to use three different hand-cursor assignments. We found that monkeys were able to perform this task in a flexible manner. This report first introduces a problem-solving framework for studying the function of the PFC, from the view point of cognitive science. Then, this chapter will cover the neuronal representation of a series of actions, goal subgoal transformation, and synchrony of PFC neurons. We reported PFC neurons reflected final goals and immediate goals during the preparatory period. We also found some PFC neurons reflected each of all forthcoming steps of actions during the preparatory period and increased their activity step by step during the execution period. Recently, we found that the transient increase in synchronous activity of PFC neurons was involved in goal subgoal transformations. Our data suggest that the PFC is involved primarily in the dynamic representation of multiple future events that occur as a consequence of behavioral actions in problem-solving situations.