Eight new spirostanol saponins (1-8) and three new furostanol saponins (9-11) were isolated from the whole plants of Agave utahensis. The structures of 1-11 were determined by analysis of extensive spectroscopic data. The saponins were evaluated for their cytotoxic activity against HL-60 human promyelocytic leukemia cells. Compound 1 showed cytotoxicity against HL-60 cells with an IC(50) value of 4.9 microg/mL, induced apoptosis in HL-60 cells, and markedly activated caspase-3.