Rates and variations of methane (CH₄) emission and production in the paddy fields in Japan were analized. CH₄ emission from paddy fields showed strong seasonal variations, depending on soil Eh, water management, and mineral fertilizer applied. The emission rate widely varied with soil types during the cultivation period. Annual emission rates from paddy fields composed of Peat soil, Gley soil, and Andosols are estimated at 44.8, 8.0-27.0, and 0.6-12.6 g-CH₄/m², respectively. Application of rice straw with rates of 6-9 t/ha increased the CH₄ emission rates by 1.8- to 3.5-fold. The CH₄ production rates of paddy soils measured under the laboratory incubation experiments also showed seasonal variations, which were well correlated with the CH₄ emission rates measured in the paddy fields. These results indicate that the seasonal variations of CH₄ emission from paddy fields to the atmosphere are mainly brought about by the variation of CH₄ production in paddy soils. However, the ratio of the production rates to the emission rates varied among soils, suggesting that physical and chemical properties of soils play a significant role for production and emission of CH₄ in the paddy fields.