In recent years, considerable progress has been made in understanding the pathogenic mechanisms involved in the allo- and autoimmune thrombocytopenias. A number of new platelet-associated alloantigens have been described and platelet autoantigens continue to be studied in more detail. Specific assays for antibodies directed against the major antigenic platelet glycoproteins are now available. Important recent clinical investigations have led to modification of the management of immune thrombocytopenia in the perinatal period, resulting in a reduced risk of hemorrhagic complications for both mother and infant. Future investigations are likely to further improve the outcome of these pregnancies.