The joint application of clinical and genetic investigation to patients with inherited thrombocytopenias, as well as the availability of new methods for studying megakaryopoiesis, has greatly expanded the knowledge of these disorders in the last few years with regard to their etiology, pathogenesis and clinical aspects. In particular, new diseases have been described, as deriving from mutations in the genes FLNA, TUBB1, ITGA2/ITGB3, ANKRD26, CYCS, and ABCG5 or ABCG8. Moreover, forms previously considered separate entities were found to be different clinical aspects of a single disease. For instance, identification of MYH9 as the gene whose mutations cause the May-Hegglin anomaly led to the recognition that Sebastian platelet syndrome, Epstein syndrome, and Fechtner syndrome derive from mutations of the same gene and describe overlapping disorders. Despite these advances, knowledge of hereditary thrombocytopenias is still far from satisfactory because for approximately half of the patients it is not possible to formulate a definite diagnosis in that their illnesses has not yet been described. In this review, we provide a systematic description of hereditary thrombocytopenias as we know them today, giving special attention to genetic aspects.