The invention relates to an improved process for preparing 3-aminomethyl-3,5,5-trimethylcyclohexylamine, referred to hereinafter as isophoronediamine or, in abbreviated form, IPDA, by: I. preparation of isophorone by catalyzed aldol condensations with acetone as reactant; II. reaction of isophorone with HCN to form isophoronenitrile (IPN, 3-cyano-3,5,5-trimethylcyclohexanone); III. catalytic hydrogenation and/or catalytic reductive amination (also referred to as aminative hydrogenation) of 3-cyano-3,5,5-trimethylcyclohexanone, hereinafter called isophoronenitrile or, in abbreviated form, IPN, to give the isophoronediamine.