PURPOSE: To provide the new oxime derivative which is effective as an inhibitor of 5-lipoxygenase and usable for treating inflammation and/or allergic disorders.

CONSTITUTION: The compound of formula I (R4 is H, alkyl, halogenoalkyl, phenyl, phenylalkyl or the like; R5 is R4, pyridyl, pyrimidinyl, furyl, thienyl or the like; Ar1 is phenylene, pyridinediyl or pyrimidinediyl, A1 is direct bond or alkylene; X1 is O, S, SO or SO2; Ar2 is Ar1, thiophenediyl, furandiyl or the like; R1-R3 are such that R1 is H, alkyl, alkenyl or alkynyl and R2 and R3 together form -A2-X2-A3-, or R1 and R2 together form -A2-X2-A3- and R3 is alkyl, alkenyl, alkynyl (A2, A3 are each alkylene; X2 is O, S, SO, SO2 or NH)], e.g. acetone O-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl) phenylthio]benzyl}oxime, is obtained by reacting the compound of formula If with the compound of formula III.