We report the results of a randomized clinical trial of two different coricosteroids (prednisone versus deflazacort) in patients affected by autoimmune thrombocytopenic purpura (ATP). We have evaluated the efficacy of the two steroids on platelet count, antiplatelet antibodies, lymphocyte subsets and the occurrence of side effects. Twenty-seven patients were evaluable: 13 were treated with PDN and 14 with DFC. After 24 weeks of treatment, 4/12 (33%), subjects treated with PDN were refractory while complete responses were obtained in 2/12 (17%) and partial responses in 6/12 (50%). Among patients treated with DFC, 4/11 (36%) were considered as refractory, 2/11 (18%) had a complete response and 5/11 (46%) a partial response. A statistically significant decrease of antiplatelet antibodies was recorded in both groups after 4 weeks of therapy, but only in subjects receiving PDN did the reduction last until the 24th week. We observed an increase of T lymphocyte subsets (CD3, CD2, CD4, CD8) in absolute number, due to an increase in circulating lymphocytes, after 4 weeks. No substantial modifications were observed in these populations regarding the percentage or the CD4/CD8 ratio. After 24 weeks, 91% (10/11) of patients treated with PDN presented an increase of body weight and 1 had a stable increase in blood pressure. Among the subjects treated with DFC, 64% (7/11) showed an increase of body weight after the same follow-up. In conclusion, no difference was observed the two steroids studied.