Therapeutic polyamines useful as a cancer chemotherapeutic agents, including molecules having a formula R.sub.1 --NH--(CH.sub.2).sub.x --NH --(CH.sub.2).sub.x --NH--(CH.sub.2).sub.y --NH--(CH.sub.2).sub.z --NH--R, wherein R.sub.1 and R.sub.2 are hydrocarbon chains having 1 to 5 carbons and w, x, y and z are integers of 1 to 10, are disclosed. One such molecule is N.sup.1, N.sup.19 -bis(ethylamino)-5,10,15-triazanonadecane, which is longer than spermine. This preferred compound may be used alone or in combination with other therapeutic agents, such as 1,3-bis(2-chloroethyl)-1-nitrosourea or cis-Pt.