The term polycythemia (literally, "many blood cell disease") and its obsolete synonym, erythremia, postdate Robert Hooke's 17th century discovery of cells, but the concept of a clinically problematic excess of blood was formulated in antiquity. Observation of plethoric patients by clinicians of the Hippocratic school informed the classical humoral framework that dominated theoretical constructs of human disease for more than a thousand years. In the golden era of disease description at the end of the 19th century, the idiopathic entity polycythemia rubra vera (PRV) was first described and distinguished from secondary and relative polycythemia (red cell excess not caused by a primary bone marrow disorder, and artifactual red cell excess caused by plasma volume contraction, respectively). This review traces some of the principal events in the history of polycythemia vera (PV) as a discrete clinical entity.