The decision support software described in the paper, the OASIS system, provides ground-water modelers with a ground-water biodegradation model, model documentation, background information, data from chemical and hydrogeologic databases, and data management tools. The system was developed using HyperCard software on a Macintosh personal computer. It currently has over 1700 different computer screens of information and occupies approximately 10 megabytes of hard disk storage. OASIS is a new type of modeling software where ground-water models, data, and knowledge are integrated together using a graphical interface and an easily modified software architecture. Two groups of users can benefit from the system: current modelers who need more efficient interfaces and data management tools, and people who are not using models now because the modeling process is too involved and requires special knowledge.