An environmental database was developed to store water-quality data collected during the 1999 U.S. Geological Survey investigation of the occurrence and distribution of dioxins, furans, and PCBs in the riverbed sediment and fish tissue in the Penobscot River in Maine. The database can be used to store a wide range of detailed information and to perform complex queries on the data it contains. The database also could be used to store data from other historical and any future environmental studies conducted on the Penobscot River and surrounding regions.