We found a tertiary methylated tetraamine, N4-methylthermospermine [NH2 (CH2)3N(CH3)(CH2)3NH (CH2)4NH2][PA 3(Me)34] in addition to spermidine, homospermidine, spermine, thermospermine and canavalmine in extracts of mature seeds of leguminous plants, Wistaria floribunda, Canavalia gladiata and Astragalus sinicus by HPLC and GC-mass spectrometry. This is the first report to show the presence of a tertiary branched methyl derivative of any polyamine.