Abstract: A highly pure, white, solid amine oxide is prepared in high yield with minimal decomposition of the solvent by (A) reacting a tert-amine with a 15-20% stoichiometric excess of concentrated hydrogen peroxide at 50.degree.-55.degree. C. in the presence of controlled amounts of carbon dioxide and ethyl acetate until the reaction mixture contains 35-45 % by weight of ethyl acetate and less than 0.8% by weight of unreacted amine, (B) catalytically decomposing residual hydrogen peroxide, (C) separating the reaction mixture from the decomposition catalyst, (D) cooling the reaction mixture to 0.degree. C. to form a slurry, (E) centrifuging the slurry to separate the amine oxide, and (F) vacuum drying the amine oxide at ambient temperature--the reaction mixture being diluted to an amine oxide content of 25-30% by weight with additional ethyl acetate or a mixture thereof with a co-solvent, such as a low-boiling n-alkane, after the completion of Step A and prior to the beginning of Step D.