Abstract The presence of pharmaceutical compounds in treated wastewater and in surface waters is a growing environmental concern. This paper provides information about general awareness of the issue, disposal practices, willingness to pay for a disposal program, and willingness to participate in a disposal program. The results are based on a telephone survey of 1005 residents in southern California. Less than half of the respondents are aware of the issue. While disposal of unused medications through the trash and toilet/sink is the most common practices, respondents that are aware of the issue are more likely to return pharmaceuticals to a pharmacy or drop them off at a hazardous waste center. The results of a contingent valuation question indicate a substantial willingness to pay a surcharge on prescriptions to support the establishment of a pharmaceutical disposal program. The more conservative estimate of mean willingness to pay is $1.53 per prescription, which translates into an average annual willingness to pay of approximately $14. A benefit-cost comparison suggests ample scope for establishing a pharmaceutical disposal program that would yield positive net social benefits, even if the surcharge was applied to only one prescription per year. We also find that respondents are likely to participate in a disposal program. Assuming that the program is based on drop-off locations at local pharmacies, approximately 70 percent of the respondents would be very likely to return their unwanted or expired medicines.