90 patients diagnosed as eosinophilia and pulmonary infiltrates with peripheral eosinophilia in PUMC Hospital from 1957 to 1986 were reported. The cause of the eosinophilia was unknown in 42% of the patients. Among these patients, hypereosinophilic syndromes (HES) were suspected in 11 patients. The most common presenting symptoms of HES were fever, skin lesions gastrointestinal symptoms and hepatosplenomegaly, the mean peripheral blood eosinophil count was as high as 25.6 x 10(9) cells/L. Biopsies of bone marrow and involved organs revealed extensive eosinophilic infiltration and severe necrosis. In the past ten years, eosinophilia and pulmonary infiltrates caused by parasitic infections obviously decreased. The most common parasites were ascaris Lumbricoides, Ancylostoma duodenale and Clonorchis sinesis. The other main causes which induced pulmonary infiltrates were allergic bronchopulmonary mycosis (ABPM) and chronic eosinophilic pneumonia. The prevalence of ABPM increased recently; early diagnosis and effective therapy could prevent the irreversible damage resulting in airways obstruction and fibrosis.