Process for preparing 3-aminomethyl-3,5,5-trimethylcyclohexylamine by I. preparation of isophorone by catalyzed aldol condensations of acetone as a reactant, workup of the reaction product, hydrolysis of the stream of value and separation into an organic fraction and an aqueous fraction, recovery of isophorone from the organic fraction, distillative workup of the aqueous fraction and passage of the vapors from the top of the distillative workup apparatus onward into the hydrolysis apparatus, wherein the water from the bottoms of the distillative workup of the aqueous fraction is subjected to a flash evaporation and the purified water which forms is recycled into the process for preparing isophorone; II. base-catalyzed reaction of isophorone with HCN to form isophoronenitrile; III. preparation of isophoronediamine by means of catalytic hydrogenation and/or catalytic reductive amination of isophoronenitrile, in the presence of ammonia, hydrogen and at least one catalyst and optionally a solvent or solvent mixture, where the cyanide ion concentration in the reaction mixture which is sent to the hydrogenation is 200 ppmw to 5000 ppmw, based on the isophoronenitrile used, wherein IPDA is prepared by a two-stage process, and wherein at least some of the isophoronenitrile used is converted in the first stage by reaction with ammonia in the presence or absence of an imination catalyst and/or of solvents to isophoronenitrileimine, the conversion of IPN to IPNI after the imination being greater than 80%, preferably greater than 90%, more preferably greater than 95%, and wherein the first stage reaction product, as obtained or after a further treatment and/or addition of further ammonia, is subjected in the second stage to aminating hydrogenation over hydrogenation catalysts in the presence of at least ammonia and hydrogen and in the presence or absence of an organic solvent at a temperature of 20 to 150°C, preferably 40 to 130°C, and a pressure of 0.3 to 50 MPa, preferably 5 to 30 MPa. I. preparation of isophorone by catalyzed aldol condensations of acetone as a reactant, workup of the reaction product, hydrolysis of the stream of value and separation into an organic fraction and an aqueous fraction, recovery of isophorone from the organic fraction, distillative workup of the aqueous fraction and passage of the vapors from the top of the distillative workup apparatus onward into the hydrolysis apparatus, wherein the water from the bottoms of the distillative workup of the aqueous fraction is subjected to a flash evaporation and the purified water which forms is recycled into the process for preparing isophorone; II. base-catalyzed reaction of isophorone with HCN to form isophoronenitrile; III. preparation of isophoronediamine by means of catalytic hydrogenation and/or catalytic reductive amination of isophoronenitrile, in the presence of ammonia, hydrogen and at least one catalyst and optionally a solvent or solvent mixture, where the cyanide ion concentration in the reaction mixture which is sent to the hydrogenation is 200 ppmw to 5000 ppmw, based on the isophoronenitrile used, wherein IPDA is prepared by a two-stage process, and wherein at least some of the isophoronenitrile used is converted in the first stage by reaction with ammonia in the presence or absence of an imination catalyst and/or of solvents to isophoronenitrileimine, the conversion of IPN to IPNI after the imination being greater than 80%, preferably greater than 90%, more preferably greater than 95%, and wherein the first stage reaction product, as obtained or after a further treatment and/or addition of further ammonia, is subjected in the second stage to aminating hydrogenation over hydrogenation catalysts in the presence of at least ammonia and hydrogen and in the presence or absence of an organic solvent at a temperature of 20 to 150°C, preferably 40 to 130°C, and a pressure of 0.3 to 50 MPa, preferably 5 to 30 MPa.