Two of the primary requirements needed for a successful study of epitaxy are a contamination free environment (UHV) and an extremely smooth, clean substrate surface. The deposition should be studied in situ by means of some surface sensitive technique (e.g. RHEED or LEED) and then in TEM and TED. Such a study has been conducted with Cu on (111) Au.Extremely smooth (111) single crystals of Au were evaporated on NaCl/mica in a UHV-RHEED system whose base pressure was 7 x 10-10 torr. After a 15 minute anneal at 625°C the films were cooled to room temperature. The initial growth of Cu on (111) Au at room temperature was studied is the following manner. Fractions of a monolayer of Cu were deposited (~1A per minute) onto the Au substrate and immediately examined in RHEED.