The present study demonstrated that the temporal integration time (t.i.t.) could be prolonged even if the background energy was increased, provided that the background consisted of the colors opponent to each other. This was found, more or less, irrespective of the test stimulus size. These results suggest that the t.i.t. is not determined solely at receptor sites in the visual system, but that the chromatically-opponent systems are heavily involved. Mechanisms based upon a two-sites adaptation with one detection pathway model were briefly discussed.