The Connecticut Hospital Association has developed a data resource for inpatient pharmacy information. The RxData project collects drug dispensing information from member hospitals and joins it to administrative discharge data in the Chime database. The resulting dataset is useful for descriptive epidemiology of drug use patterns as well as surveillance, quality improvement, and some hypothesis testing. The drug identity is derived from the National Drug Code submitted by hospital pharmacies. A drug reference file is used together with these codes for hierarchical analysis. Data are accepted from participating facilities in a variety of formats and mapped to a common schema. The program uses locally developed roll-up logic to overcome the lack of consistent standards for recording inpatient drug order and dispense information. Dispensing records at different levels of aggregation are collected from source pharmacy information systems and converted to a standard "regimen" based on continuous dispensing of the same drug. The resulting record structure allows direct comparison of data from dissimilar systems. Data are currently available for eleven acute care hospitals and most of their associated emergency and outpatient surgery facilities. The program is expected to expand to cover most if not all Connecticut hospitals over the next two to three years.