The authors employed free-air carbon dioxide enrichment facilities for investigating the effects of elevating the present atmospheric CO2 by 200 ¿mol mol-1 and increasing the application rate of urea-based fertilizers from 150 to 250 kg N ha-1 on CH4 emissions from paddy rice fields in southeastern China. The elevated CO2 significantly stimulated methane emission, which was mainly due to the stimulation in rice growth. Intensifying N fertilization mitigated the CH4 emission under the ambient CO2 but stimulated the CH4 emission under the elevated CO2. This suggests that N fertilization has a potential to stimulate both CH4 production and CH4 oxidation. Thus the net effect of N fertilization on CH4 emission from paddy rice fields most likely depends upon the counterbalance between the nitrogen-induced increases in CH4 production and CH4 oxidation, as a N excess may result in the inhibition of methane emission, whereas a N limitation may result in the stimulation of methane emission.