Thirteen compounds were isolated from the anomalous fruits of Gleditsia sinensis on the basis of bioassay-guided fractionation. These saponins together with six analogues or related compounds were tested for their cytotoxicities against six tumor cell lines by the MTT method. The induction of apoptosis in HL-60 cells by these compounds was determined through flow cytometric analysis. Some structure-activity relationships in cytotoxicity and induction of apoptosis were identified. The evaluation of the cytotoxicity and the ability to induce apoptosis revealed that some important structural features are required for activity. A valuable model which enables prediction of their activities was established and may be employed for the drug design of new Gleditsia saponin analogues.