The alkaloid composition of leaves of Lupinus linearis Desr. (3 ecotypes) and L. gibertia nus Smith (6 ecotypes) from Argentina and Brazil were studied by capillary gas-liquid chromatography and GLC-mass spectrometry (EI-MS). Both species are closely related according to morphological criteria. This view is supported by the alkaloid profiles which are very similar and share a series of new and uncommon alkaloids. Main alkaloids are lupanine, 13-hydroxylupanine, esters of 13-hydroxylupanine (e.g. 13-angeloyloxylupanine, 13-tigloyloxylupanine, 13-benzoyloxylupanine, 13-cis/trans-cinnamoyloxylupanine). Minor alkaloids are: sparteine, 11,12 -dehydrosparteine, ammodendrine, tetrahydrorhom bifoline, angustifoline, α-isolupanine, 5,6-dehydrolupanine, 11,12-dehydrolupanine, N-formylangustifoline, 13-cis-cinnamoyloxymultiflorine. New minor alkaloids which have been tentatively identified by GLC-MS are 13-hydroxy-17-oxolupanine and corresponding esters (13-an-geloyloxy-17-oxolupanine, 13-tigloyloxy-17-oxolupanine, 13-benzoyloxy-17-oxolupanine, 13-cis-cinnamoyloxy-17-oxolupanine, and 13-trans-cinnamoyloxy-17-oxolupanine).