The stability of ursodiol in an extemporaneously formulated oral liquid was studied. A suspension was prepared by combining the contents of commercially available 300-mg capsules of ursodiol with glycerin, Ora-Plus (Paddock Laboratories), and orange syrup. A second formulation was prepared by combining ursodiol capsules with sterile water for irrigation. The final concentration of ursodiol in each formulation was 25 mg/mL. Six samples of each preparation were stored in 4-oz amber plastic prescription bottles protected from light. Three were stored at 22-23 degrees C and three were refrigerated at 2-6 degrees C. Immediately after preparation and at 7, 15, 30, 45, and 60 days, samples were obtained and frozen until assay by high-performance liquid chromatography. On day 60 the mean percentage of the initial ursodiol concentration remaining was 108.4% for the suspension stored at room temperature and 103.3% for the refrigerated suspension. The ursodiolin-water formulation was not analyzed because of rapid settling of ursodiol. Ursodiol 25 mg/mL in an oral liquid prepared extemporaneously from capsules and sweetened vehicle was stable for 60 days when stored in amber plastic bottles at 22-23 and 2-6 degrees C. Addition of ursodiol powder to water without a suspending agent resulted in a liquid formulation with a high variability in content uniformity.