The stability of ursodiol in an extemporaneous oral liquid formulation refrigerated at 4 degrees C for 35 days was studied. A suspension was prepared by opening commercially available 300-mg capsules of ursodiol, adding Glycerin, USP, to form a paste, and then adding Simple Syrup, NF. A control solution was prepared from analytical-grade ursodiol powder in simple syrup. The final concentration of ursodiol in both formulations was 60 mg/mL. Three samples of each preparation were stored in 2-oz, amber glass prescription bottles in the dark at 4 degrees C. Immediately after preparation and at 7, 14, 21, 28, and 35 days, samples were visually inspected, tested for pH, and assayed in duplicate by high-performance liquid chromatography. Stability was defined as the retention of more than 90% of the initial concentration. On day 35, the mean percentage of the initial ursodiol concentration remaining was 96.5% in the suspension made from powder-filled capsules, and 100.6% in the suspension made from analytical-grade powder. The color, odor, and pH of the samples did not change appreciably over the study period. An extemporaneously compounded oral liquid preparation of ursodiol in simple syrup was stable under the conditions studied for up to 35 days.