The purpose of this study was to investigate the effects of music tempi on music preference, intrinsic motivation, and flow during long-duration exercise (approximately 26 min). Subjects (n = 29) selected the music of a single artist then walked at 70 % of maximum heart rate reserve (maxHRR) on a treadmill under three experimental conditions (medium tempi, fast tempi, and mixed tempi) and a no-music control. A music preference item, the Intrinsic Motivation Inventory, and Flow State Scale-2 were completed after each trial. Data were analyzed using a mixed-model (Gender x Condition) ANOVA and MANOVA. The Gender x Condition interaction was nonsignificant in both analyses (p > 0.05). Contrary to expectations, higher preference scores were recorded for medium tempi than for mixed tempi (means: 7.8 +/- 1.3 vs. 7.1 +/- 1.1). The medium tempi music also yielded the highest levels of intrinsic motivation (p < 0.001). Pairwise comparisons showed that interest-enjoyment was higher for medium tempi when compared to mixed tempi, 95% CI = 1.80-8.48, p = 0.001, and that each of the music preference experimental conditions yielded higher scores than the no-music control. Also, pressure-tension was lower for medium tempi compared to fast tempi, 95% CI = -3.44-0.19, p = 0.022, and for both medium and mixed tempi compared to control (95% CI = -5.33-2.89, p = 0.000; 95% CI = -4.24 - 0.64, p = 0.004). A main effect was found for global flow (p = 0.000) with the highest mean score evident in the medium tempi condition (14.6 +/- 1.5). Follow-up comparisons indicated that the medium tempi condition yielded higher flow scores than the control, 95% CI = 1.25-3.60, p = 0.000, as did fast tempi, 95% CI = 0.89-3.14, p = 0.000, and mixed tempi, 95% CI = 1.36-3.76, p = 0.000. It was concluded that a medium tempi music program was the most appropriate for an exercise intensity of 70% maxHRR.