POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes) syndrome is a rare variant of plasma cell dyscrasia with multiple systemic manifestations. We followed the progress of 20 patients with POEMS syndrome in our institution over a 10-yr period. Pulmonary hypertension (PH) was observed in five patients. All patients suffered dyspnea on exertion, which always appeared during an exacerbation of POEMS syndrome. The typical echocardiographic signs of PH were observed in all of these patients, and the median pulmonary-artery systolic pressure was 57 mm Hg (range, 50 to 65 mm Hg). Mean pulmonary-artery pressure during right side heart catheterization in two patients was 32 mm Hg. No other explanation for the PH could be found. Overproduction of cytokines was found in all cases, with high serum concentrations of interleukin-1beta, interleukin-6, tumor necrosis factor-alpha, and vascular endothelial growth factor. We suggest that PH should be added to the list of symptoms of POEMS syndrome. Cytokines may mediate POEMS syndrome-associated PH, as proposed for the other systemic manifestations of this disorder.