The invention comprises N-acyl derivatives of iminodibenzyl of the formula: <FORM:0715424/IV (b)/1> or salts thereof with organic or inorganic acids, wherein X represents a divalent saturated aliphatic radical containing not more than five carbon atoms and Am represents the radical of a secondary amine consisting of NH and two aliphatic hydrocarbon radicals, each containing not more than five carbon atoms, the radical of a tri-(lower alkyl)-ethylene-diamine, the lower alkyl radical containing not more than three carbon atoms, or the radical of an alkylene imine having five or six ring members. The compounds are prepared by reacting an N-(halogenalkanoyl)-iminodibenzyl, produced by acylating iminodibenzyl with reactive halogen fatty acid derivatives, with a secondary amine consisting of NH and two aliphatic hydrogen radicals, each containing not more than five carbon atoms, with a tri-(lower alkyl)-ethylene diamine, the lower alkyl radical containing not more than three carbon atoms, or with an alkylene imine having five or six ring members, in an inert solvent (e.g. benzene or homologues thereof) and in presence of an acid-binding agent such as an organic tertiary base (e.g. dimethyl aniline or pyridine), a suitable inorganic binding agent (e.g. sodium or potassium carbonate) or an excess of the amine used for the reaction. Lists of suitable starting materials are specified. The examples describe the preparation of N-(a -diethylamino-propionyl) - iminodibenzyl, N - (a - piperidino-propionyl) - iminodibenzyl, N - [a - (N1 - di-methylaminoethyl - N1 - methyl - amino)-propionyl] - iminodibenzyl, N - a - (pyrrolidino-propionyl) - iminodibenzyl, N - (a - dimethyl-amino - butyryl) - iminodibenzyl, N - [a - (di-ethylaminoethyl - N1 - ethyl - amino) - butyryl]-iminodibenzyl, N - (a - piperidino - butyryl)-iminodibenzyl, N - (dimethylamino - acetyl)-iminodibenzyl, N - (diethylamino - acetyl)-iminodibenzyl, N - (N1 - diethylaminoethyl-N1-ethylamino - acetyl) - iminodibenzyl, N - di-allyl - aminoacetyl - iminodibenzyl, N - dibutylaminoacetyl - iminodibenzyl, N - piperidinoacetyl - iminodibenzyl, N - (a - dimethylamino-propionyl) - iminodibenzyl, N - (b - dimethylamino - propionyl) - iminodibenzyl, N - (b -diethylamino - propionyl) - iminodibenzyl, N-(b - piperidino - propionyl) - iminodibenzyl, N - (b - diallylamino - propionyl) - iminodibenzyl, N - [b - (N1 - diethylaminoethyl - N1-ethylamino) - propionyl] - iminodibenzyl, N-(b - dimethylamino - butyryl) - iminodibenzyl, N - (b - pyrrolidino - butyryl) - iminodibenzyl, and N - [b - (N1 - dimethylaminoethyl - N1-methylamino) - butyryl] - iminodibenzyl. N - (halogen - alkanoyl) - iminodibenzyls are prepared by acylating iminodibenzyl with halogen fatty acid halides or the corresponding anhydrides in the presence or absence of, for example, pyridine or dimethyl aniline. The following are prepared or employed as starting materials in the examples: N-chloracetyl-, N-a - bromopropionyl -, N - a - bromobutyryl -, N - b - bromopropionyl -, and N - b - bromobutyryl-iminodibenzyl. Others are mentioned as suitable starting materials.