The prefrontal cortex is critical for temporal organization of behavior. It mediates cross-temporal sensory-motor contingencies, integrating motor action (including speech) with recent sensory information. It performs this role through cooperation of two cognitive functions represented in its dorsolateral areas: short-term memory (STM) and preparatory set. Supporting data have been obtained from monkeys performing delay tasks, which epitomize the principle of cross-temporal contingency. In a given trial, the animal performs an act contingent on a sensory cue given a few seconds or minutes earlier. During the delay between cue and response, cells in dorsolateral prefrontal cortex show sustained activation. Two cell categories can be identified in tasks in which cue and response are spatially separate. Cells of the first participate in STM: Their activation tends to diminish as the delay progresses; in some, the activation level depends on the particular cue received. Similar cells are found elsewhere in cortex. Cells of the second category seem to take part in preparation of motor response: Their activation tends to increase in anticipation of it and may be attuned to the particular movement the cue calls for. This cell type is rare outside of frontal cortex. The temporally integrative function of the prefrontal cortex is probably based on local interactions between "memory" and "motor-set" cells, as well as on neural associations between prefrontal cortex and posterior cortical areas.