1. Five oxazolidines were synthesized by reaction of (-) ephedrine with formaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde, and acetone, respectively. 2. Half-lives of hydrolysis were measured in pH 7.4 aqueous buffer. Half-lives varied from 12 seconds to 11 minutes. 3. The compounds were evaluated for their ability to increase locomotor activity in rats. All compounds significantly increased locomotor activity at 50 mg/kg dose. 4. The formaldehyde derivative had similar activity to (-) ephedrine. All other compounds were less active than (-) ephedrine.