Glucocorticoids have been used widely in conjunction with other treatment for patients with cancer because they have potent proapoptotic properties in lymphoid cells, can reduce nausea, and alleviate acute toxic effects in healthy tissue. However, glucocorticoids are used in a supportive-care role, even though to our knowledge no prospective clinical studies have assessed the effect of these steroids on the growth of solid tumours. Data from preclinical and, to some extent, clinical studies, suggest that glucocorticoids induce treatment resistance in solid tumours, including prostate cancer. Research has focussed on disseminated cells that have been shed by the tumour: the potential of glucocorticoids to render these cells resistant to apoptosis--and to downregulate the immune response--might contribute to tumour metastasis. Here, we review the benefits of glucocorticoids and their negative effects, such as induction of resistance in tumour cells and concomitant induction of apoptosis in immune cells, with particular emphasis on prostate cancer.