This study investigated medical waste practices used by hospitals in Oregon, Washington, and Idaho, which includes the majority of hospitals in the U.S. Environmental Protection Agency's (EPA) Region 10. During the fall of 1993, 225 hospitals were surveyed with a response rate of 72.5%. The results reported here focus on infectious waste segregation practices, medical waste treatment and disposal practices, and the operating status of hospital incinerators in these three states. Hospitals were provided a definition of medical waste in the survey, but were queried about how they define infectious waste. The results implied that there was no consensus about which agency or organization's definition of infectious waste should be used in their waste management programs. Confusion around the definition of infectious waste may also have contributed to the finding that almost half of the IMPLICATIONS The disposal and treatment of medical waste continues to be a topic of controversy and concern, particularly since air pollution standards have forced the closure of many hospital incinerators. This research provides the first comprehensive overview of medical waste treatment and disposal practices being used by the majority of hospitals in EPA Region 10, and updated information about the effect clean air regulations have had in forcing these hospitals to consider alternative medical waste management strategies. As the overall volume and costs associated with treatment continue to increase, this information is important to generators of medical waste, hospitals outside this region, state agencies that are involved in the regulatory processes, and waste management companies that treat medical waste generated by any type of healthcare facility.