Abstract: The invention relates to muramyleptide derivatives resulting essentially from the conjugation or the coupling, as the case may require, through an arm, between a muramylpeptide and a group containing two atoms contiguous with one another to each of which is attached a lipophile chain comprising from 8 to 100 carbon atoms, preferably from 14 to 24 carbon atoms. The derivatives according to the invention are endowed with remarkable stimulating properties with respect to the activation of macrophages, of which they amplify the tumoricidal properties.