We have developed a three-dimensional model to study global methane distributions and the transport of methane. The model includes transports, chemical reactions, and global methane sources. The calculations provide a fairly good simulation of the observed latitudinal gradient of methane and its global mean distribution in the stratosphere. The model results also suggest that rice paddies in Southeast Asia and wetlands in the high latitudes of North America can contribute to required sources for maximum of methane. The simulation also models the positive vertical gradients of methane in the troposphere of the southern hemisphere, which was observed by Fraser et al. (1984). The model analyses show that this positive gradient is the result of the interhemispheric transport of methane at upper levels of the troposphere. ¿American Geophysical Union 1991