With a micro-computer-gravicorder SG-1, the Length/Time (LNG/T), Root Mean Square (RMS) and Standard Deviation Area (SD-Area) of body sway were analyzed automatically in 14 kinds of visual and somatosensory condition. The test was done in 22 normal subjects (NS) and 55 patients with vertebrobasilar insuffiency who were classified into 6 groups by the results of caloric testing.Eighteen kinds of calculation and statistical analyses were done with a computer to compose NS and each patient group. All the groups showed different chara-cteristic body sways under different external condi-tions.1) In the NS group, body sway in the dark>body sway while looking at OKN>body sway while watching LED≅body sway in the light.2) In group A, the SD-Area of body sway while watching LED was larger than in the dark on the S-G board.3) In group B, the RMS and the SD-Area in the dark was smaller than while looking at OKN, while watching LED or in the light on the S-G board. The RMS while watching LED was larger than in the dark or while looking at OKN on the flat board.4) In group D, the LNG/T while watching LED was larger than while looking at OKN on both boards.5) In group E, there were no characteristic findings. With those tests, we could demonstrate the effects of visualvestibular-somatosensory interactions on body sway.