Platinum and silicon have been found deposited on the palladium cathode during the electrolysis of a 0.1 M LiOD solution with a platinum anode in a glass cell. Various techniques including surface analysis, cyclic voltammetry, and electrochemical permeation were used to study the surface deposits, electrochemical deuterium-sorption behavior, and permeation rate of deuterium into palladium, respectively. It was shown that palladium cathodes were contaminated by platinum and silicon deposits after a certain period of electrolysis. These deposits could affect the electrochemical processes during electrolysis. The contamination may be a cause of the sporadic results reported in “cold fusion” research.