The stability of ondansetron hydrochloride 0.24 and 2 mg/mL when delivered by portable infusion pump at near-body temperature over various time periods was investigated. Nine 100-mL drug reservoirs were prepared, three containing ondansetron hydrochloride 2 mg/mL and six containing ondansetron hydrochloride diluted with 0.9% sodium chloride injection to 0.24 mg/mL. Three of the reservoirs containing the diluted solution were refrigerated for up to 30 days at 3 degrees C before being attached to portable infusion pumps and pumped over 24 hours at 30 degrees C. The remaining six reservoirs were attached to pumps immediately after being filled, and the solutions were delivered for up to 24 hours (the diluted solution; three reservoirs) or up to seven days (the concentrated solution; three reservoirs) at 30 degrees C. Samples were taken initially and periodically and analyzed by high-performance liquid chromatography and with a pH meter. Both the diluted and the concentrated solutions of ondansetron hydrochloride retained at least 95% of the initial drug concentration under all the conditions studied. There was no appreciable change in pH. Ondansetron hydrochloride 0.24 mg/mL was stable when stored for up to 30 days at 3 degrees C and infused over 24 hours at 30 degrees C. Ondansetron hydrochloride 2 mg/mL was stable when infused for up to one week at 30 degrees C.