A 34-year-old woman with asthma had increasing dyspnea on exertion for 9 months and new-onset mononeuritis multiplex. An examination demonstrated sinus tachycardia, elevated jugular venous pressure, and a tender nonpulsatile liver. The leukocyte count was 15.8 x 10(9)/L, with 23% eosinophils. Echocardiography revealed a laminated thrombus obliterating much of the right ventricular cavity, with encasement of the tricuspid valve. Ultrafast computed tomography showed no evidence of pulmonary emboli. Biopsy specimens of skin nodules revealed extravascular palisading granulomas. The thrombus was refractory to corticosteroids, and right ventricular thrombectomy was performed. To our knowledge, this is the third reported case of Churg-Strauss syndrome with thrombotic complications from coexistent eosinophilic endomyocarditis. In an asthmatic patient with chronic dyspnea, eosinophilic tissue infiltration, and neuropathy, Churg-Strauss syndrome should be considered; evaluation for cardiac involvement may be warranted.