Low levels of secretary IgA (sIgA) have been associated with recurrent upper respiratory tract infection (URTI) (Gleeson et al., 1999). Saliva contains approximately 60% sIgA1 and 40% sIgA2 in normal adults (Tappuni & Challacombe, 1994). Because sIgA1 is more susceptible to proteases degradation produced by mucosal pathogens, the higher the proportion of sIgA1 and the lower the sIgA2 concentration, may increase the risk of bacterial mucosal infection (Kilian et al., 1996). The aim of the present study is to investigate the effects of acute prolonged intensive exercise on saliva flow rate, sIgA level, and sIgA1/sIgA ratio. Following approval by the local Ethics Committee, eight male volunteers (age 21.3 ± 1.0 years, body mass 66.8 ± 2.0 kg, VO2max 52.5 ± 2.1 mL.kg-1.min-1, peak power 259 ± 6 watt; means ± SEM) performed either a single bout of cycling at 55% peak power for 2 h (started at 9:00) or a separate resting trial separated by at least a week in a counterbalanced design. Timed, unstimulated saliva samples and venous blood samples were obtained at 10 min before exercise (Pre-EX), the last 2 min of exercise (Post-EX), and 1 h (P-EX-1h) and 2 h (P-EX-2h, saliva only) after exercise. Water ingestion was allowed ad libitum during the trials except for the 5 min preceding each saliva sample collection. The concentrations of sIgA and sIgA1 were determined by ELISA. Results were analyzed using a two-factor (trial × time) repeated measures ANOVA with post hoc Tukey tests and paired t tests applied where appropriate. The results of this study showed that a 2-h cycling at 55% peak power significantly decreased blood glucose concentration (P<0.01) and increased plasma concentrations of cortisol and adrenaline (both P<0.01) as shown in Table 1. However, there were no significant effects on saliva flow rate, sIgA level, and sIgA1/sIgA ratio. These findings suggested that a single bout of cycling at 55% peak power for 2 h does not appear to acutely affect oral immunity.