Tumor-associated hypoglycemia as a paraneoplastic phenomenon is a well-known entity and is referred to as Doege-Potter syndrome. A man was admitted because of acute confusion and drowsiness. Laboratory results showed profound hypoglycemia. All investigations proved to be normal, except for a chest x-ray, which showed a large pleural mass. On transthoracic puncture, a tumor of pleural origin was diagnosed. This tumor, presenting as a large, well-circumscribed encapsulated mass, was removed by thoracotomy. On pathologic examination, the diagnosis of a solitary fibrous tumor with benign characteristics was made. After surgical removal, the hypoglycemia resolved. Solitary fibrous tumors are localized tumors of the pleura with an unpredictable behavior. The therapy consists of resection.