Recent reports have suggested that running economy (RE) defined as oxygen consumption at standardized treadmill speeds may be an important determinant for successful distance running performance. The purpose of this study was to examine the additional role, if any, played by anaerobic factors in distance running performance. Highly trained male cross-country runners (N = 12) were administered a battery of standardized aerobic and anaerobic laboratory evaluations. Maximal oxygen uptake (VO2max) and RE (ml X kg-1) were measured using open circuit spirometry during treadmill exercise. RE was measured at 241 and 295 m X min-1, and ventilatory threshold (Tvent) was determined and verified using a number of non-invasive ventilatory measures (VE, VE/VO2, VE/VCO2, VCO2, FECO2). Anaerobic measures included the Margaria power test and the Monod critical power test to determine anaerobic work capacity (AWC). The data were subjected to a SAS-STEPWISE analysis which combines stepwise addition and backward elimination and were used to predict performance time in a 8.05-km (5-mile) cross-country race in which all the runners participated. The subjects averaged 26.21 min for the 8.05 km run, with 72.1 ml X kg-1 X min-1 for the VO2max with a Tvent at 60.4 ml X kg-1 X min-1 (84% VO2max). AWC (Monod) was 17400 Joules with a range of 8,000-28,400 Joules. The STEPWISE procedure reveals that AWC contributes significantly (P less than 0.003) to a 3 variable model predicting race performance (R2 = 0.76, P less than 0.01). AWC accounts for 58% of total shared variance with VO2max and an indirect measure of Tvent accounting for the remaining 17%.(ABSTRACT TRUNCATED AT 250 WORDS)