OBJECTIVE: To compare the surface electromyographic activity of the abdominal musculature and rectus femoris (RF) muscle during trunk-flexion exercises using 3 abdominal exercise devices (Ab Roller, ABslide, and FitBall) and the traditional trunk curl. DESIGN AND SETTING: Each subject performed approximately 15 repetitions for each exercise condition. A repeated-measures, one-way multivariate analysis of variance was used to compare the mean integrated electric activity value for each muscle during each exercise condition. SUBJECTS: A total of 10 male and 13 female collegiate undergraduate students. MEASUREMENTS: Surface electromyographic activity was recorded for the upper rectus abdominis (URA), lower rectus abdominis (LRA), external oblique (EO), and RF during 5 consecutive repetitions of each exercise bout. The signal was amplified by a factor of 1000, rectified, and integrated. These integrated values were then divided by the time value for each exercise to give the mean integrated electromyography value. RESULTS: A significant difference existed among exercise conditions for the RF (P <.0001), with the ABslide and the FitBall having greater electric activity than the other exercise conditions. Activity was significantly different (P <.0009) for the URA, with the ABslide having the least electric activity. For the EO, exercising with the ABslide produced significantly greater electric activity (P <.0001) than all other exercise conditions. No significant difference was found across exercise conditions for the LRA (P <.051). CONCLUSIONS: Performing abdominal exercises with the Ab Roller, ABslide, and FitBall did not elicit greater activity of the URA and LRA than performing traditional trunk curls. Use of the ABslide elicited greater EO activity and significantly less URA activity than the other 3 modes. Both the ABslide and FitBall resulted in greater involvement of the hip flexors, an undesirable feature of abdominal exercises.