The existing molecular biology databases focus on the sequence and structural aspects of biological macromolecules, i.e. DNAs, RNAs and proteins. However, in order to understand the functional aspects, it is essential to computerize the interaction of these molecules. Furthermore, living cells contain additional molecules, such as metabolic compounds and metal ions, that may also be considered as parts of the basic building blocks of life, but are not well organized in public databases. LIGAND chemical database is our attempt to solve these problems, at least for enzymatic reactions.