This invention relates to combination chemotherapy, particularly involving vitamin D or a derivative thereof hi one aspect, the invention provides a method of killing a cell by first administering to the cell vitamin D (or a derivative) and subsequently administering to the cell a cytotoxic agent. Where this strategy is applied to an intact tumor, the present invention provides a method of retarding the growth of the tumor by first administering vitamin D (or a derivative) to the tumor and subsequently administering the cytotoxic agent. A further aspect of the invention concerns a method of treating prostate cancer within a patient by co-administration of vitamin D (or a derivative) and a glucocorticoid to the patient. In yet a further aspect, the invention provides an improved method of treating a patient with vitamin-D involving the adjunctive administration of zoledronate.