Forty-three operative procedures were performed on a population of 250 patients with myeloproliferative disorders, including polycythemia vera, myeloid metaplasia (MM) and chronic myelogenous leukemia (CML). The overall operative mortality was approximately 7% and the incidence of excessive bleeding which could be related to coagulopathy was 5%. Twenty-one patients with MM or CML underwent splenectomy for palliation of symptoms related to the enlarged spleen or hematologic problems. Eighty-four percent of the latter group were improved. Adverse hematologic effects which could be attributed to splenectomy in these patients were confined to two patients who developed marked thrombocytosis. Among the 23 patients with MM, 9 had portal hypertension. Three underwent portacaval shunt and one a splenorenal shunt for bleeding varices. One of the patients died of hepatic necrosis. Estimated hepatic blood flow determinations (EHBF) in 4 patients with portal hypertension demonstrated a marked absolute increase and an increase in the ratio of EHBF/Cardiac Index. Absence of any evidence of intrahepatic or extrahepatic obstruction in these patients and the demonstration that splenectomy relieved portal hypertension defined at surgery in 4 patients, suggests that augmented adhepatic flow contributes to portal hypertension in some cases. The review leads to the conclusions that: 1) Operative procedures in prepared patients with myeloproliferative disorders are not associated with prohibitive mortality and morbidity rates. 2) Splenectomy is indicated for patients with increasing transfusion requirements and symptomatic splenomegaly or hypersplenism and should be performed early in the course of disease. 3) When associated portal hypertension and bleeding varices are present, hemodynamic studies should be carried out to define if splenectomy alone, or a portal systemic decompressive procedure is indicated.