Oxiranes are made from ketones by heating a ketone which is preferably an alkyl ketone to a temperature of from about 60.degree. to about 90.degree. C. (preferably about 80.degree. C.) in the presence of a sulfonium salt, a quaternary ammonium salt and a potassium hydroxide solution which is at least 61% potassium hydroxide. It is preferred that no organic solvent be included in the reaction mixture. The potassium hydroxide is generally included in an amount such that for every mole of ketone, from about 3 to about 4 moles of potassium hydroxide are present. The sulfonium salt is generally used in an amount of at least 1.1 moles for each mole of ketone. The quaternary ammonium salt is generally used in an amount of from about 1 to about 5 mol % based on moles of ketone present.