AbstractInformation is given as to the rates of peroxidation of diethyl ether and di‐isopropyl ether under normal laboratory conditions of storage, both with and without inhibitors. Di‐isopropyl ether peroxidizes in daylight at least twice as rapidly, and in the dark several times as rapidly, as diethyl ether. By storing di‐isopropyl ether over 20% caustic soda the ether layer can be maintained almost free from peroxide. Anti‐oxidants effectively protect di‐isopropyl ether for limited periods. Diethyl ether can be protected from peroxidation by storage in presence of iron, and can be largely protected merely by storage in the dark.It is proposed in this paper to review briefly the more recent literature dealing with the peroxidation and avoidance of peroxidation of diethyl and di‐isopropyl ethers and to record our own observations under both