In agreement with previous reports, we found that dexamethasone may induce radioresistance in human carcinoma cells. Including the published data from the literature, dexamethasone induced enhancement in radioresistance in 4 of 12 carcinoma cell lines (33%), but not in 3 glioblastoma cell lines, nor in 3 fibroblast strains. Dexamethasone also induced enhanced resistance to carboplatin with a similar probability in fresh samples of ovarian cancer evaluated prospectively (in 4 of 13 samples; 31%). We worry that induction of resistance by corticosteroids given to patients undergoing either radiotherapy or chemotherapy with agents causing DNA damage might be associated with a reduced clinical responsiveness in a significant fraction of patients with a carcinoma.