Abstract: A ventilation air intake structure of a motor vehicle is shown, which comprises two side panels incorporated with both a cowl top panel and a dash upper panel to define an air box which extends along a rear upper edge portion of an engine room of the vehicle. The cowl top panel has a first opening and the dash upper panel has a second opening which is communicated with a passenger cabin of the motor vehicle. A drain chamber is constituted by the hood ridge reinforcing member and one of the side panels. The drain chamber has a downwardly extending narrower passage which is exposed to the open air at a terminal open end thereof. The dash upper panel is formed with a laterally extending channel which has a shallower end portion which passes under the side panel and is exposed at its terminal end to the narrower passage at a position above the terminal open end of the downwardly extending narrower passage.