Design patterns raise the abstraction level at which people design and communicate design of object-oriented software. But design patterns still leave the mechanics of their implementation to the programmer. This paper describes the architecture and implementation of a tool that automates the implementation of design patterns. The user of the tool supplies application-specific information for a given pattern, from which the tool generates all the pattern-prescribed code automatically. The tool has a distributed architecture that lends itself to implementation with off-the-shelf components.