Cellular retroreflective sheeting, which comprises a base layer of retroreflective elements and a transparent cover film supported in spaced relation away from the base layer by a network of narrow intersecting bonds that form hermetically sealed cells within which retroreflective elements are isolated from retroreflective elements of different cells, is given greater durability by use of bonds that are cured in situ after they have been thermoformed into sealing contact between the cover film and base layer.