The authors sought to, analyze the time course of human stereopsis process, and focused on the measurement of VEP. The evoked response in stereopsis has been considered as a single component appearing with a latency of approximately 200 ms, but it has recently been revealed that the response is composed of two components with different properties. This paper discusses the relation between the second latency range in the two-peaked response and the figure-ground process. The characteristics of the figure-ground stimulus are defined and examined by the size ratio of the single rectangular region (figure) of the random-dot stereogram with binocular disparity to, the background (ground). As a result, two successively generated negative components are observed. Of those, the initial component of the latency of approximately 150 ms increases the response with the absolute amount of stimulus, and is independent of the size ratio to the background. The second component with a latency of approximately 250 ms exhibits a stronger response when the figure region is narrowed. The response decreased with increase of the stimulus size, and disappeared when the whole stimulus was uniform. The above tendency of the response is verified, independently of the kind of local cue that defines the figure region. These results indicate that the second component has a strong correlation to the figure-ground process, and also the latency range related to the binocular fusion is located before the occurrence of the second component. A discussion of the neural mechanism underlying the two-peaked response is also presented, from the viewpoints of the relative delay of the second component and the local cue-independent continuous response modulation. (C) 2003 Wiley Periodicals, Inc.