1. Any etching, either chemical or electrical, sufficient to remove an adequate bulk of metal from the tissue surface of a casting will have a measurable and, hence, adverse effect on the margins of the restoration. 2. During any etching process, all margins and contact and occluding surfaces should be protected. 3. For aqua regia etching, Type 2 inlay wax appeared to provide sufficient protection. For electrochemical milling, fingernail polish appeared to provide sufficient protection. 4. Ceramco gold exhibited more resistance to the action of both electrochemical milling and aqua regia etching than did the "C" bridge alloy. 5. Aqua regia etching required more time than electrochemical milling on the two types of gold tested.