This study investigated whether sprint triathlon performance can be adequately predicted from laboratory tests. Ten triathletes [mean (SEM), age 21.8 (0.3) years, height 179 (2) cm, body mass 67.5 (2.5) kg] performed two graded maximal exercise test in random order, either on their own bicycle which was mounted on an ergometer or on a treadmill, to determine their peak oxygen consumption (V̇O2peak). Furthermore, they participated in two to three 30-min constant-load tests in both swimming, cycling and running to establish their maximal lactate steady state (MLSS) in each exercise mode. Swim tests were performed in a 25-m swimming pool (water temperature 27°C). During each test heart rate (HR), power output (PO) or running/swimming speed and blood lactate concentration (BLC) were recorded at regular intervals. Oxygen uptake (V̇O2) was continuously measured during the graded tests. Two weeks after the laboratory tests all subjects competed in a triathlon race (500 m swim, 20-km bike, 5-km run) [1 h 4 min 45 s (1 min 38 s)]. Peak HR was 7 beats·min−1 lower in the graded cycle test than in the treadmill test (p<0.05) at similar peak BLC (~10 mmol·l−1) and V̇O2peak (~5 L·min−1). High correlations were found between V̇O2peak during cycling (r=−0.71, p<0.05) or running (r=−0.69, p<0.05) and triathlon performance. Stepwise multiple regression analysis showed that running speed and swimming speed at MLSS, together with BLC in running at MLSS, yielded the best prediction of performance [1 h 5 min 18 s (1 min 49 s)]. Thus, our data indicate that exercise tests aimed to determine MLSS in running and swimming allow for a precise estimation of sprint triathlon performance.