The aim of this study was to evaluate the importance of anaerobic metabolism as a determinant of individual differences in performance of a 1-mile run-walk (MRW). Anaerobic capacity, percentage of anaerobic capacity used during the MRW, percentage of energy used during the MRW that was supplied through anaerobic processes, aerobic metabolic determinants of distance running performance, and MRW time were measured in 26 male and 29 female young adult nonathletes. Anaerobic processes averaged 7-8% of the energy used during the MRW. In multiple regression analyses, anaerobic capacity, and a linear combination of all three anaerobic variables contributed significantly to the prediction of MRW with the effects of gender and [Formula: see text] peak held constant, but the additional variance accounted for by the anaerobic variables was relatively small (2-7%). In conclusion, anaerobic metabolism supplies only a small portion of the energy used during the MRW, and anaerobic capacity and metabolism during the MRW do not confound its interpretation as an indicator of maximal aerobic power in a heterogeneous group of young men and women of moderate fitness level. Key words: energy metabolism, oxygen deficit, physical fitness, running performance