The objective of this project is to develop a database of chemical structures which can be used for full structure and substructure searching of chemical substances of toxicological, occupational and hazardous concerns. The initial phase of this project will utilize the CHEMBASE software developed by Molecular Design Limited to establish this capability for a PC-based chemical structure database. As the size of the structure database increases, this structure searching system will be upgraded to an online system operable on a microcomputer.