Technical Abstract: Soil quality and the ability of soil to sustain nutrient cycling in reclaimed soils will influence the subsequent establishment and maintenance of a permanent and stable plant community. We undertook an experiment using a recently developed "three-day CO2 flush method" to compare a range of soil biological indicators across a series of reclaimed, surface coal-mined sites in the Powder River Basin of northeastern Wyoming. In addition, we were interested in estimating the amount of soil organic carbon (SOC) required to sustain nutrient cycling. Soils were sampled from each of two different reclaimed sites on four different mines in 2000. In 2001 we sampled soils from three sites on three mines - two reclaimed and a native, undisturbed prairie control site. For both years, soils were dried, rewetted, and microbial respiration measured at three and 21 days, using base trap methods. In addition, microbial biomass, nitrogen (N)-mineralization, organic carbon (C) and total N were measured. Regression analyses were accomplished by regressing three-day microbial respiration against the other soil parameters measured. Correlations between three-day microbial respiration and all of the measured soil parameters were generally strong (r2 = 0.55) and highly significant (P < 0.0001). There were differences between the reclaimed and native sites; the native sites exhibited more variability (although still significantly correlated), probably due to either differences in the relative lability of the substrates present or differences in the structure of the microbial communities present in the native versus reclaimed soils. We believe this method is of use as a relatively fast, accurate, and economical means by which soil quality can be ascertained. Estimates of SOC required to sustain nutrient cycling appears to be in the upper range of 0.1-0.7% C.