A 51-year-old man was admitted to our hospital because of dry cough an
d low grade fever with right-sided pleural fluid and blood eosinophili
a. Warfarin had been prescribed following coronary artery bypass graft
ing. After the discontinuation of warfarin the clinical and chest X-ra
y findings improved; readministration of the drug caused recurrent blo
od eosinophilia and pleural effusion in the other lung. Since no other
specific etiologies for eosinophilia and pleural effusion were determ
ined by extensive evaluation, warfarin seemed to be associated with hi
s illness. This is the first report of warfarin-induced eosinophilic p
leurisy.