The term ‘idiopathic neutropenia’ describes various types of neutropenia that may occur at any point in life for unknown reasons. Therefore onset of idiopathic neutropenia is possible in both, children and adults. As already described for the other types of neutropenia, frequency and severity of infections is correlated with the neutrophil counts. Neutrophil counts and clinical problems in these patients vary considerably, but in general those patients with the more severe neutropenia have more frequent infections. Most patients respond well to G-CSF treatment but require long-term treatment.