Abstract: A vehicle rooftop storage unit includes a rack portion which is permanently installed to the roof of the passenger vehicle at manufacture, or which may be installed as an aftermarket article after vehicle manufacture. A separate container portion is removably securable within the rack portion. The rack portion includes a generally rectangular rail, with the front and side members being fixed in position, and the rear member being hinged to the rear end of one of the side members. The rear member may be locked to the opposite side member to close the rail structure, and thereby capture the container portion within the rack rails. The rack portion captures the container portion by a tongue formed along the inner face of the rail, which engages a mating peripheral groove in the container portion; the tongue and groove configuration may be reversed between container and rack rail, if desired.