Objective The long-term clinical course and prognosis of patients with chronic eosinophilic pneumonia (CEP) including factors predictive of the relapse of CEP have not been fully investigated. The aim of the present study was to investigate these issues. Methods We retrospectively investigated the rate of relapse and prognosis in 73 patients diagnosed as having CEP. Results Systemic corticosteroid therapy was administered at a prednisolone dose of 29.4±7.6 mg/day. During a median follow-up period of 1,939 days, 27 patients suffered from relapse of CEP. Two patients developed steroid-induced diabetes mellitus, and 1 patient developed pulmonary nontuberculous mycobacteriosis. Five patients died; however, none died of CEP. A history of smoking was the only independent negative risk factor for relapse of CEP [hazard ratio, 0.37 (0.14-0.98)]. Conclusion Patients with CEP frequently relapse. During the follow-up, metabolic and infectious complications under prolonged corticosteroid therapy are problematic. A history of smoking was a negative factor for predicting the risk of CEP relapse.