Drugs induce a variety of pulmonary diseases including pulmonary infiltration with eosinophilia (PIE) syndrome. We report a case of PIE syndrome which was observed after neck dissection. An 83-year-old male patient attended our clinic complaining of upper neck swelling and was diagnosed as advanced lymph node metastasis related to previously resected oral carcinoma and underwent neck dissection. Despite administration of antibiotics (piperacillin sodium, PIPC; and tosufloxacin tosilate, TFLX), fever and an elevation of the c-reactive protein (CRP) level with neutrophilia appeared, and an infiltration shadow was observed in the right lower pulmonary field. With the suspicion of pneumonia, the antibiotics were exchanged for panipenem/betamipron. However, the pulmonary infiltration spread widely, CRP increased to 12.9 mg/dl and severe eosinophilia (23%) was observed a few days after changing the antibiotics. PIE syndrome was suspected, and the patient underwent steroid mini-pulse therapy consisting of methylprednisolone sodium succinate (500 mg) and prednisolone (60 mg). After steroid therapy, the pulmonary condition largely improved. However, about 2 weeks after the start of steroid administration, a fever and a further elevation of CRP were observed with an increase of beta -D-glucan in serum. Roentgenography revealed diffuse infiltration shadows throughout the lungs, and the patient died about 3 weeks after the onset from respiratory distress. In vitro, blastogenesis of patient's peripheral blood lymphocytes was strongly enhanced by PIPC and TFLX, and they generated a large amount of interleukin-5 in the presence of PIPC or TFLX. The clinical course and laboratory examination results revealed that PIE syndrome may have been induced by PIPC and TFLX and that PIE syndrome should be suspected in treatment of carcinomas when dyspnea and pulmonary infiltration are complicated with eosinophilia. (C) 2001 Elsevier Science Ltd. All rights reserved.