The stability of clonidine hydrochloride in an extemporaneous oral liquid formulation refrigerated for 28 days was studied. A suspension was prepared by grinding commercially available 0.2-mg clonidine hydrochloride tablets, adding Purified Water, USP, to form a paste, and then adding Simple Syrup, NF. A control solution was prepared from analytical grade clonidine hydrochloride powder in Simple Syrup, NF. The final concentration of clonidine hydrochloride in both formulations was 0.1 mg/mL. Three samples of each preparation were stored in 2-ounce amber glass prescription bottles in the dark at 4 degrees C. Immediately after preparation and at 3, 7, 14, 21, and 28 days, samples were visually inspected, tested for pH, and assayed in duplicate by high-performance liquid chromatography. On day 28, the mean percentages of the initial clonidine hydrochloride concentrations remaining were 92.4% in the suspension and 93.7% in the solution. The color, odor, and pH of the samples did not change appreciably over the study period. An extemporaneously compounded oral liquid preparation of clonidine hydrochloride in Simple Syrup, NF, is stable under the conditions studied for up to 28 days.