A large number of adventures and supplements were published for Classical D&D over the years. Most are usable with any version of Classical D&D without major modification and can easily be used with Original D&D or First Edition AD&D with only a little effort from the gamemaster. The major exception to this is the Immortals modules which really only work well with the Immortals Set of the BECMI version of Classical D&D.

For the most part, TSR adventures for Classical D&D were divided into series based on rules set. B-series modules only needed basic Set rules, X-series modules required the Expert Set, C-series modules were for use with the Companion Set, M-series modules were for use with the Masters Set, and the above-mentioned IM-series modules were for use with BECMI Immortals Set.