Dehydrochlorination of an aqueous solution of propylene chlorohydrin with sodium hydroxide (12.5 and 30% by weight), with catholyte (5 or 10% by weight NaOH + 14% by weight NaCl) and with milk of lime (15% by weight) were compared. The use of catholyte (10% by weight NaOH + 14% by weight NaCl) enables propylene oxide to be obtained in a yield of 94.3%, with 100% conversion of chlorohydrin. The concentration of 1,2-propylene glycol in the waste is 0.07% by weight.