The standard molecular data (SMD) format is described, providing a powerful tool for data exchange between chemically oriented programs. By its modular design it offers a broad application range and great flexibility with respect to future extensions; Le., definition of new information blocks is possible without affecting existing blocks. Furthermore, the SMD format includes the concept of superatom-representing subsets of a molecular structure or ensemblewhich offers a new strategy for economic and flexible storage of large molecules (proteins, polymers, etc.) and permits a new and consistent method for storage of reactions. This paper is not intended to be a technical report on the format, but the basic ideas and strategies guiding its design are presented.