Vegetation composition and grazing by livestock have significant effects on soil respiration rates. An objective of this study was to determine how different cropping systems and livestock grazing might influence soil respiration rates in an integrated livestock and grain crop agroecosystem. Soil respiration rates were measured using a LiCor 6400 11 times from May to December 2004 in two row crop systems and two pasture types at the Dudley Smith research farm in central Illinois. The row crop systems consisted of a conventional corn-soybean rotation and a small grain-corn rotation with cover crops that were grazed during winter. The two pasture types consisted of cool season grasses and native, warm season grasses. Corresponding environmental variables and soil microbial biomass were also measured. Soil respiration rates in all pastures and cropping systems were highest in spring and declined to almost zero in winter. Respiration rates ranged from 0.39-6.56, 0.91-6.84, 0.76-5.11, and 0.50-5.76 µmol CO2 m-2 s-1 in the conventional corn-soybean rotation, small grain-corn rotation, cool season grass pastures, and warm season grass pastures, respectively. Respiration rates were higher in the small grain-corn rotation in spring. This cropping system had cover crops that were grazed by cattle during the winter. Cover crops and manure inputs by cattle may have contributed to a larger labile carbon pool that stimulated decomposition and soil respiration during this period. The cool season grass pastures showed higher soil respiration rates during the fall and winter possibly due to higher root turnover. Preliminary conclusions suggest that soil respiration rates differ among the row crop and pasture systems but only at certain times during the year. The cumulative CO2 flux from soils was relatively similar among row crop and pasture systems, however.