The stability of aminophylline and fluconazole in intravenous admixtures containing both drugs was studied. Admixtures containing aminophylline 2.0 or 1.0 mg/mL and fluconazole 1.5 or 0.5 mg/mL in 5% dextrose injection or 0.9% sodium chloride injection were prepared. Each admixture was prepared in triplicate in glass containers and kept at 24 degrees C. Immediately after preparation and at one, two, and three hours, samples were visually inspected, tested for pH, and assayed in duplicate by high-performance liquid chromatography for theophylline concentration and fluconazole concentration. More than 98% of the initial aminophylline and fluconazole concentrations remained at each test interval. There was no visible evidence of precipitation, gas formation, or color change. No appreciable change in pH occurred during the study period. Aminophylline 1.0-2.0 mg/mL and fluconazole 0.5-1.5 mg/mL admixed in 5% dextrose injection or 0.9% sodium chloride injection were stable and compatible for up to three hours at 24 degrees C.