The patient was a 45-year-old woman in whom a chest X-ray film obtained on admission showed bilateral infiltrative shadows. A chest CT scan revealed areas of consolidation and ground-glass opacities. Examination of bronchoalveolar lavage fluid revealed many eosinophils, and specimens obtained by transbronchial lung biopsy showed thickened alveolar septa with infiltration of eosinophils. The numbers of eosinophils and the level of IgE in blood were low. The radiographic appearance improved after administration of suplatast tosilate. The level of interleukin 5 was high both in plasma and in bronchoalveolar lavage fluid before treatment, but the level of IL-5 in plasma was low after suplatast tosilate was given. Suplatast tosilate, which suppresses the production of cytokines, may be useful in patients with chronic eosinophilic pneumonia.