The administration of glucocorticoids and immune suppressives, as well as the splenectomy, are conisered the standard treatment of idiopathic thrombocytopenic purpura (ITP). In the last few years, however, the indications have increased that the use of vincristine sulphate (VCR)-at least in individual cases-can lead to a significant increase in the number of thrombocytes. On the basis of a therapeutic study with VCR presented herein, the value of this treatment method is investigated. 13 patients with a chronic, previously therapy-resistant form of ITP were treated with VCR. Weekly applications of 1.0 mg/m2 VCR for a maximum 6 weeks led in 2 cases to a temporary normalization of the thrombocyte values, and in 2 other cases to a short-term subnormal increase in the thrombocyte values. The advantages and disadvantages of VCR treatment are discussed by comparing the results of our study with the information presented in the literature. The author's conclusion is that VCR is too ineffective in the treatment of ITP, and the risks too high, to recommend it for general use. Therefore, the problem of treating specifically the chronic type of ITP remains unsolved.