A method of information processing in a server/client system including a server for storing content and a client for receiving from the server and storing copy content of the content stored in the server. The method includes the steps of: the server generating at least either a content-ID list storing content-IDs corresponding to content for which use-expiration-date updating is permitted out of the copy content stored in the client or a content-ID list storing content-IDs corresponding to content for which use-expiration-date updating is not permitted, transmitting the content-ID list to the client; and the client selectively performing update processing of use-expiration date out of the copy content stored in that client or invalidation processing of the copy content stored in that client based on the content-ID list received from the server.