-The objective of this work was to evaluate the effect of two legumes (Crotalaria juncea and Mucuna pruriens), as cover crops, and of natural fallow, as a control treatment, on the emissions of NO x , N 2 O, and CO 2 from an Oxisol cultivated with corn, under conventional and no-tillage systems, in the Cerrado region, in Central Brazil. Variations of CO 2 fluxes in the soil were explained mainly by soil humidity and, in the legumes, under conventional system, by soil NH 4 + -N concentration. Plots with legumes under no-tillage system had higher annual emissions of CO 2 , NO x , and N 2 O than natural fallow. Results show that the use of legumes as cover crops favors the emissions of NO x -N + N 2 O-N and CO 2 -C. However, when considering the potential for mitigation of CO 2 and nitrogen oxide emissions from the soil, it is important to evaluate changes in soil carbon and nitrogen stocks.