The fatty acid oxygenase of sheep vesicular glands was solubilized with Tween-40 and purified 60-fold using ammonium sulfate precipitation and Deae-cellulose chromatography. Glycerol (50%) stabilized the activity at all stages of purification and allowed long-term storage at -60 degrees. The partially purified enzyme contained less than 0.7 nmoles of iron per mg of protein and less than 0.1 nmole of copper per mg of protein. Although the KI values for aspirin, BL-2338, flurbiprofen and ibuprofen remained relatively unchanged during purification, the apparent KI value for inhibition by indomethacin decreased from 120 to 2.7 muM.