This study examined the effect of a 10-min, halftime cooling application on physiological and psychological parameters known to affect performance. Fourteen volunteers (10 male, 4 female) completed two randomised trials 48 hr to 7 days apart. Trials consisted of a 1-hr cycling protocol: 30 min at 75% VO2max followed by 10 min cooling (application of a cooling jacket) or passive recovery (control), and a second 30-min exercise bout consisting of 20 min at 75% VO2max, immediately followed by a 10-min maximal effort, where work was measured as energy expended (kJ). Performance of the 10-min maximal intensity phase tended to improve (171.5 +/- 30.4 kJ vs 165.4 +/- 29.2 kJ, p = 0.087) following the cooling trial. Heart rate during the 5th min of the maximal effort, (183 +/- 9 beats.min(-1) vs 180 +/- 7 beats.min(-1), p = 0.024), blood lactate concentration at 6 min post-exercise (9.3 +/- 3.1 mmolxL(-1) vs 7.9 +/- 3.2 mmolxL(-1), p = 0.007), rating of perceived exertion at the 20th min post-halftime recovery (15 +/- 2 vs 16 +/- 2, p = 0.042), and subjective rating of feelings and emotions differed between the cooling and control conditions. Sweat loss, core and mean skin temperature and rating of thermal sensation failed to differ significantly between conditions. Halftime cooling tended to result in greater aerobic performance. Psychological assessment revealed a dramatic placebo effect from the cooling application confounding these results. Furthermore, the cooling intervention failed to induce any significant thermoregulatory effects.