Abstract The surfaces of ice and naphthalene crystals have been studied by low-energy electron diffraction (LEED). The crystals were grown by vapor phase epitaxy on a clean Pt(111) substrate, and the surface orientations are the ab (001) plane of naphthalene and a hexagonal sheet of ice [fcc (111) or hep (0001)]. The surface structures of both molecular crystals are unreconstructed. Ordered surfaces could be obtained only in a finite temperature range (125–155 K for ice and 105–200K for naphthalene) and were markedly dependent on substrate cleanliness and order. Electron beam damage and charging of the molecular surfaces were observed, but did not prevent characterization of the surface structures of sufficiently thin (less than 10 3 Å) crystalline films.