Visual after-effects experienced after prolonged viewing of a stimulus have been successfully used to reveal principles of visual functioning. The goal of the study was to determine how information passed through local cortical filters is integrated into global patterns. Colour-contingent after-effect, McCollough Effect (ME) (1) was used for this purpose.ME implies that as a result of alternating adaptation to vertical black-red and horizontal black-green gratings, vertical white strips of test black-white grating are perceived as greenish, while horizontal ones as reddish. We aimed to resolve the question whether ME is specific to local retinotopic components or is dependent on global spatiotopic patterns. Neurophysiological studies have indicated, that spatial extent of cortical filters selective to different spatial frequencies and orientations is limited (2). Though other studies (3) point to global factors responsible for the effect, ME is somewhat specific to retinal area, orientation and size (4). Acquisition of ME results in changes of the colour discrimination thresholds measured with anomaloscope (5). Five observers examined with standard visual tests (Landolt Acuity test, Farnsworth-Munsell D-15 test, Ishihara^,s Peudoisochromatic Plates, Nagel Anomaloscopy) participated. They were presented with horizontal black-red and vertical black-green gratings (spatial frequency 5 cycle/degree), displayed on a computer screen 30°x 40° for two minutes. After such adaptation all the participants acquired clear-cut central ME. Afterwards, gratings 4°x5°of angular size, of the same orientation and of opponent colour to the gratings presented earlier, were presented to the observers in the peripheral visual field (7° of eccentricity). Two types of combined stimuli were used for testing: central and peripheral, which contained achromatic gratings of both orientations. Four observers experienced peripheral ME: phantom colours observed on both test stimuli were dependent on the location of the gratings. Colours were less saturated on the periphery and were opponent. The data obtained let us conclude that global information incoming from the whole visual field determine the genesis of ME and information incoming from different regions is processed separately and summarized later.