We successfully treated three cases of adult Still's disease (ASD) with dexamethasone. High dose prednisolone, which was initially used to treat these patients, failed to remit the disease in all cases. Although they were resistant to prednisolone, all these patients had remarkable improvements in clinical and laboratory findings after switching to an equivalent dose of dexamethasone. We propose using dexamethasone as an alternative for treating ASD before adding immunosuppressants or disease modifying anti-rheumatic drugs (DMARD), when prednisolone therapy does not suppress disease activity sufficiently.