The compatibility of cefoperazone sodium and furosemide in 5% dextrose injection stored at two temperatures was studied. Cefoperazone sodium and furosemide were added to 5% dextrose injection to achieve a cefoperazone concentration of 10 mg/mL and a furosemide concentration of 0.2 mg/mL. The admixture was stored in 100-mL vented i.v. containers in the dark under refrigeration (4 degrees C) and at room temperature (25 degrees C); three containers were stored at each temperature. A 1-mL sample was taken from each i.v. container immediately after preparation and after 1, 2, 5, 10, 15, 20, and 25 days to be inspected visually, checked for pH value, and analyzed by a stability-indicating high-performance liquid chromatographic method. No color change or precipitation was observed in any sample at any time during the study. More than 95% of the initial concentrations of both drugs remained for five days at 4 degrees C but for only two days at 25 degrees C. Cefoperazone sodium was somewhat more stable than furosemide under the same storage conditions for 25 days; however, less than a 2% difference between the drugs was noted. Under the conditions of this study, cefoperazone sodium 10 mg/mL and furosemide 0.2 mg/mL in admixtures in 5% dextrose injection are stable for only two days at 25 degrees C and five days at 4 degrees C.