BACKGROUND: The purpose of this study was to evaluate the inter-day reliability of the IPRO method for determining resting and postexercise salivary cortisol (sCort) and rate of salivary Immunoglobulin-A (sIgA) secretion. METHODS: Fourteen males (32±11 years) performed two trials (T1 and T2) separated by 7 d, comprising saliva sampling before and 15 min after completion of two, 30-s Wingate Anaerobic Tests separated by 3.5 min (2 x WAnT). sCort increased after the 2 x WAnT in both trials (T1: P<0.001; T2: P<0.001), whereas rate of sIgA secretion decreased in both trials (T1: P=0.002; T2: P=0.002). RESULTS: The intraclass correlation coefficients for resting and postexercise sCort and rate of sIgA secretion ranged from 0.96-0.99. Mean reliability, expressed as the coefficient of variation (%) and the typical error of measurement over the two trials were resting sCort 9.4%, 0.14 ng·mL-1 (9% CI: 0.1-0.2), postexercise sCort 11.9%, 0.44 ng·mL-1 (9% CI: 0.3-0.7), resting rate of sIgA secretion 7.4%, 85.5 µg·mL-1·min-1 (9% CI: 65.2-127.1) and postexercise rate of sIgA secretion 10.5%, 82.9 µg·mL-1·min-1 (9% CI: 63.2-123.1). CONCLUSIONS: The IPRO is a reliable method for determining sCort and rate of sIgA secretion at rest and after sprint-cycling exercise.