This paper examines how an efficient code migration component for mobile agents can be designed, an aspect crucial to the migration performance and thus, for the overall performance of such a system. Therefore, after listing the require ments of code migration in this area, and a description of the code migration mechanisms of the Java applet model, a more appropriate approach is proposed. This new approach uses two mechanisms to transport code: one that is able to get classes in an efficient manner and one that is able to get any valid class by its ref erence. Both mechanisms use a code replacement policy that is able to handle a space restricted class storage. Finally the approach uses digital signatures to pro tect the code migration component, the codeserver, against modification attacks.