Developmental changes of dominance of visual field was evaluated using a tachistoscope in 70 normal subjects from 4 years of age up to adulthood (35 males and 35 females). The time of exposure was measured under two experimental conditions; simultaneous stimulation of different types to both left and right fields, or a single stimulus only to one visual field. One of the following stimuli was exposed to the visual field; one, two or three letters of Japanese characters ("hirakana"), one of Chinese characters ("kanji"), figures, and Roman alphabets. Simultaneous bilateral stimulation revealed frequent dominance in the right visual field, which was established by 4 years of age. The average time of exposure become shorter with age up to 6-7 years for one "hirakana" letter and one "kanji", and up to 10 years for two and three "hirakana" letters. All four left-handed subjects in this study showed dominance of the right visual field. Dominance of the left visual field was observed in 3 of 52 subjects with dominance of the right eye (5.8%), and in 5 of 15 with dominance of the left eye (33.3%). This difference was statistically significant (chi 2 = 8.41, p less than 0.01). It was suggested that dominance of the visual field was related with dominance of the eye, and not with handedness.