Ten years ago the American Society of Hematology published immune (or idiopathic) thrombocytopenic purpura (ITP) practice guidelines based upon a systematic and comprehensive review of the literature.1 The authors acknowledged that hematologists regularly faced clinical management decisions with too little published scientific information about the natural history of ITP. Many of the treatments employed in ITP had been discovered empirically, and therapeutic choices were often guided by published results in case series of selected patients without a control group. Today, a decade later, we benefit from work by many investigators addressing the natural history of ITP and the pathogenic mechanisms contributing to autoimmune platelet destruction. Practice guidelines and a number of expert and consensus opinions in the literature have better defined the field.2-6 The recent era has also brought reports of new prospective clinical trials including multicenter, randomized studies that promise better guidance for the clinical hematologist in the 21st century. Recent clinical investigations of ITP assess outcome measures in addition to platelet count increments including quality of life, 7 severity of bleeding, 8 and complications of therapy. In addition, there are published reports of systematic analyses that help interpret previous literature. Hypothesis-driven studies of ITP patients and experimental animal models have also improved our understanding of the basic cellular and molecular immune mechanisms that contribute to ITP and have thus revealed new therapeutic opportunities.The present contribution will cover some of the recent basic research that has advanced our understanding of the pathogenesis of ITP and will highlight some of the clinical trials that offer insights into the diagnosis, natural history, and management of ITP in adults and children. Promising new therapeutic modalities for chronic refractory ITP will be discussed. Emphasis is placed upon explicitly designed trials. Several important clinical topics could not be included: secondary ITP, immune thrombocytopenia in pregnancy and infancy, the role of viral infection in ITP, and drug-related thrombocytopenia. Space limitations and edi-