Direct evidence, using reflection high‐energy electron diffraction, is found for a transition, at a specific thickness, from an amorphous to a crystalline state in Sb deposited on GaAs(110). After crystallization, Sb exists as small, 30–40 A˚ crystallites with a (0001) contact plane but randomly azimuthally oriented. A new surface phase, GaAs(110)p(3×2)‐Sb, is found and appears to be a consequence of the crystallization transition.