To obtain a carrier polymer for pharmacologically active components, linear polyethyleneimine (LPEI) was chemically modified by reactions with acrylic acid (1a), acrylamide (1b), acrylic acid esters (1c and 1d), sodium chloroacetate, and hydrochloric acid. All product polymers 2a – 2e are soluble in water. Among these, 2a and 2e, β- and α-amino acid derivatives, respectively, show no acute toxicity in mice up to dosages of 1 g/kg i. v. Similar types of polymers 5a and 5b and a polymer containing phosphonic acid moieties (5d) derived from branched polyethyleneimine (BPEI) were prepared. 5a and 5b are also nontoxic regardless of the molecular weight of four kinds of BPEI and of the wide range…