Disclosed is an LED fixture with passive cooling. The fixture includes a plurality of elongated tubes, each containing an array of LEDs mounted on a respective first surface or surfaces of one or more circuit boards. A frame mounts to a building structure and holds the ends of the tubes. Each tube is sufficiently spaced from any adjacent tube and from any other structure of the frame, and the frame is sufficiently open at the top and bottom, whereby heat from the tubes is capable of being dissipated merely by passive thermal transfer into an air flow created by the heat of the tubes, which air flow moves from beneath the tubes to above the tubes.