Beryllium windows, 76 mm diam and 0.25 mm thick, were joined to stainless−steel flanges by electroplating the joint area with nickel. The procedures for surface preparation of both materials and the technique used for joining the materials with nickel are described. Electroplated joints made with this method have proved to be vacuum tight to helium. By using this technique, shrinkage stresses, distortion, and recrystallization problems associated with high−temperature joining processes are eliminated.