The quinolizidine alkaloid composition of Lupinus mutabilis seeds was studied by high-resolution capillary gas-liquid chromatography (GLC) and capillary GLC-mass spectrometry. The occurrence of the known alkaloids sparteine, lupanine, α-isolupanine, 4-hydroxylupanine, and 13-hydroxylupanine was confirmed. In addition, more than 20 other alkaloids were present, including tetrahydrorhombifoline (6), angustifoline (7), multiflorine (12), 13-(angeloyloxy)lupanine (20), 13-(tigloyloxy)lupanine (21), 13-(benzoyloxy)lupanine (25), cis-13-(cinnamoyloxy)lupanine (26), trans-13-(cinnamoyloxy)lupanine (27), and ammodendrine (3). Other alkaloids were tentatively identified as 4,13-dihydroxylupanine (16), 4-(angeloyloxy)lupanine (23), and 13-(angeloyloxy)-4-hydroxylupanine (22). The quantitative composition of the alkaloid fraction is discussed with respect to the use of debittered seeds for human nutrition.