Aims: This study was designed to explore the plasma oxytocin (OT) response to exercise until exhaustion in trained male cyclists. Methods: Twelve professional cyclists (EXP group; age: 26 ± 2 years; VO<sub>2</sub>max: 4,804 ± 549 ml) and 10 sedentary young men (CONT group; age: 23 ± 2 years; VO<sub>2</sub>max: 3,146 ± 602 ml) performed a maximal incremental exercise test on a cycle ergometer. Evaluation was made of the oxygen uptake (VO<sub>2</sub>) and concentrations of blood lactate and plasma OT immediately before, during and immediately after the tests, respectively. Results: Significant increases (p < 0.01) related to exercise were recorded in VO<sub>2</sub> and lactate concentration within each group, while no such changes were observed in OT levels. OT values, on the other hand, were significantly lower (p < 0.01) in EXP than in CONT throughout the tests. Conclusion: It was concluded that plasma OT shows no response to graded exercise until exhaustion in professional cyclists.