The stability of norfloxacin in an extemporaneously prepared suspension stored at room temperature and under refrigeration was studied over 56 days. A 20-mg/mL suspension was prepared from commercially available 400-mg norfloxacin tablets and equal amounts of Ora-Plus and strawberry syrup to make a final volume of 60 mL. Six identical samples of the suspension were prepared in amber plastic prescription bottles. Three were stored at room temperature (23-25 degrees C) and three under refrigeration (3-5 degrees C). Immediately after preparation and at 7, 14, 28, and 56 days, the samples were assayed in duplicate by stability-indicating high performance liquid chromatography. The samples were also inspected for color and odor changes and the pH of each sample was determined. At least 93% of the initial norfloxacin concentration remained throughout the 56-day study period. The color, odor, and pH of all of the samples did not change appreciably. An extemporaneously prepared suspension of norfloxacin 20 mg/mL was stable for at least 56 days when stored at either 23-25 or 3-5 degrees C.