The history of and improvements made to the University of Michigan Health System (UMHS) inpatient online formulary are described. The current formulary at UMHS is the third version of the Web-based formulary. The original effort in 1997 consisted of converting word-processing documents to HTML format and exporting this information to the university's intranet. There was no mechanism to search for formulary items, no therapeutic class cross-referencing, and no cost information. Documents and their conversion had to be manually maintained. The second version incorporated a series of automatic daily computer downloads from the inpatient pharmacy computer system. Web pages were built to dynamically display the formulary information from the database based on users' requests. The formulary enabled searching by brand or generic names, provided therapeutic category cross-references, listed the location of products within automated dispensing cabinets, provided accurate cost information, and was always up-to-date. Maintenance efforts drastically decreased. The current version has incorporated additional logic to meet users' needs. If no matches are found, the system expands its search by automatically linking to UMHS's inpatient pharmacy system repository of all drugs, finding matches to what the user entered, and then returning the names of therapeutically similar formulary agents to the user. A cross-index feature allows the system to return all the drugs that fall under the searched therapeutic category. Dramatic improvements have been made to UMHS's inpatient online formulary in the past two years. The current formulary provides a very low-cost, easily maintainable, and effective means to access the formulary and clinically relevant and timely information specific to each medication.