Pulmonary hypertension associated with increased pulmonary vascular resistance occurring in the setting of portal hypertension, referred to as "portopulmonary hypertension", is a complication of chronic liver disease, and occurs in 2% to 3% of patients with portal hypertension. Portal hypertension is a relatively common finding in patients with chronic myeloproliferative disorder (CMPD). Pulmonary hypertension is also an occasional finding in CMPD patients. Latent myeloproliferative disorder, on the other hand does not fulfill the diagnostic criteria of classical CMPD and is characterized by younger age of onset, slow disease progression, a high risk of thrombosis, platelet dysfunction, and normal or increased platelet count in spite of the presence of splenomegaly. We report findings in a 50-year-old woman with portal hypertension for which there were three major etiological findings-increased splenic blood flow, infiltration of hematopoietic cells in the liver, and thrombosis in the portal or hepatic vein-over a 25-year clinical course, during which there was also reversible stenosis of the portal vein. Twenty-three years after her first admission, her condition was diagnosed as latent myeloproliferative disorder, and she developed pulmonary hypertension. Her clinical history and data indicated that the portopulmonary hypertension was due to the latent myeloproliferative disorder.