Novel cationic amphiphiles are provided that facilitate transport of biologically active molecules into cells. Typically, the amphiphiles contain lipophilic groups derived from steroids or from mono or dialkylamines, and two cationic groups, protonatable at physiological pH, derived from amines, alkylamines or polyalkylamines. There are provided also therapeutic compositions prepared typically by contacting a dispersion of one or more cationic amphiphiles, with or without colipids, and therapeutic molecules. Therapeutic molecules that can be delivered into cells according to the practice of the invention include DNA, RNA, polypeptides and low molecular weight organic compounds. Representative uses of the therapeutic compositions of the invention include providing gene therapy, and delivery of antisense polynucleotides or biologically active polypeptides to cells.