Nucleic acids transfer into mammalian cells requires devices to improve their escape from endocytic vesicles where they are mainly confined following cellular uptake. In this review, we describe histidine-rich molecules that enable the transfer of plasmid and oligonucleotides (ODN) in human and non-human cultured cells. An histidine-rich peptide which permeabilizes biological membrane at pH 6.4, favored the transfection mediated by lactosylated polylysine/pDNA complexes. Histidylated polylysine forms cationic particles of 100 nm with a plasmid and yielded a transfection of 3-4.5 orders of magnitude higher than polylysine. The biological activity of antisense ODN was increased more than 20-fold when it was complexed with highly histidylated oligolysine into small cationic spherical particles of 35 nm. Evidence that imidazole protonation mediates the effect of these molecules in endosomes are provided. We also describe a disulfide-containing polylysine conjugate capable of mediating DNA unpackaging in a reductive medium and to increase the transfection efficiency. Overall, these molecules constitute interesting devices for developing non-viral gene delivery systems.