Paroxysmal cold hemoglobinuria (hereafter abbreviated PCH) is a relatively rare clinical syndrome first described in 1854 by Dressler and 30 years later etiologically related to syphilis by Goetz. In 1904, Donath and Landsteiner1 demonstrated the presence of warm-cold type autohemolysins in the plasma of 3 patients with cold hemoglobinuria, which in all probability accounted for their hemolysis. These observations were subsequently incorporated in the test bearing their name. The typical form of the disease is associated with syphilitic infection, and the paroxysms are frequently lessened or eliminated following treatment with antisyphilitic drugs. An attack usually follows exposure to cold by minutes to several hours and is most commonly introduced by muscular crampings and headache, hyperpyrexia, and the passage of dark-red to black urine which in exceptions may last for greater than 24 hours. There may be associated urticaria and extremity cyanosis. Transient splenomegaly is not infrequent, and overt icterus