Although human parvovirus B19 (PVB19) is mainly known to be the causative agent of fifth disease, it is also important in the etiopathogenesis of various hematologic disorders. Recently, its role in the occurrence of chronic anemia and pancytopenia in immunocompromised patients has been revealed. In this study, the authors searched for the presence of PVB19 in a group of patients with idiopathic thrombocytopenic purpura (ITP). The PVB19 DNA was determined by nested PCR, and serologic responses to the virus were evaluated by ELISA. Viral genome was detected by PCR in the sera of 9 of the 19 patients. The IgM and IgG positivities were 57 and 73% in the patients, respectively. These results suggest that PVB19 is associated with ITP nearly in half of the patients and its pathogenetic role in the cases of ITP needs further consideration.