We report 3 cases of occupational hypersensitivity pneumonitis in citrus farmers. They were admitted to our hospital with abnormal chest shadows with coughs, fevers and breathlessness between January and February, but their symptoms disappeared with isolation from their workplace. The diagnoses were comprehensively confirmed by their occupational histories, radiological findings, and the positive findings of environmental provocation tests. Although we cannot clearly determine the pathogenic antigen of this hypersensitivity pneumonitis, Aspergillus and Penicillium might be the causative agents, because they were detected in the patients' workplaces and in double immunodiffusion tests. In Ouchterlony's immunodiffusion test, these antigens were positive in some patients.