A curious/unique rice dieback called “Suitou-Hagare-Shou” has been observed at paddy fields in Nagasaki Prefecture. We surveyed rice growth/dieback and environmental factors in the field, and experimented rice damage by some factors with environment-controlled growth cabinets, in order to analyze the mechanisms and to clarify the causal factors of this rice dieback. The growth and visible injury of rice plants ‘Ikuhikari’ were studied with 2 week-exposure to fog (pH3.3 or 5.6) followed by O₃ exposure (40 or 0 ppb) for 2 weeks. Visible injuries as edge/tip-chlorosis observed on rice leaves exposed to acidic fog followed by 40 ppb O₃ were similar to the symptoms of rice dieback in paddy fields. Both acidic fog and O₃ increased the visible injuries, while the extent of injury caused by fog+O₃ was remarkably higher than those by other treatments. For dry weight growth, significant decreases were observed in plants with fogs of pH3.3 relative to pH5.6, whereas almost no significance was detected between plants treated with or without O₃. The sensitivity of visible injury among rice cultivars was similar to those observed in the fields.