The Roche (handspring and double salto forward tucked) is one of the most difficult and high-risk vaults performed by elite gymnasts today. Significance: On-horse and post-flight mechanical variables have "causal influence" on the subsequent landing and overall performance of the vault. The purpose of the study was to determine the on-horse and post-flight mechanical variables that are crucial in achieving success of the Roche vault. Design: The subjects were 23 male gymnasts from 12 countries performing the Roche vault at the 2000 Olympic Games. The vaults were filmed by a 16-mm camera operating at 100 Hz. Approximately 85 frames of film were digitized for each vault. A theoretical model was developed to identify the mechanical variables that govern the linear and angular motions of the vault. Correlational analysis was used to establish the strength of the relationship between the causal mechanical variables identified in the model and the judges' score. Results: Significant correlations ( r >.30, P < .08) identified the following as important determinants of success: (1) large horizontal, vertical, and resultant velocities and great height of body’s center of mass (CM) at take-off from the horse; (2) large ‘relative height of take-off of post-flight,’ i.e., small downward vertical displacement of body CM from the ‘horse take-off’ to ‘mat landing’; and (3) great height of body CM at touchdown on the landing mat. Conclusions: Success of the Roche vault is most likely when the focus is on achieving: (a) large horizontal, vertical, and resultant velocities and high body CM at take-off from the horse (by initially sprinting the approach and, then, vigorously pushing off the horse downward with the muscles of the shoulder and shoulder girdle from high body angle near the handstand); (b) large ‘relative height of take-off’ (by completing the required number of somersaults quickly in mid-flight by flexing the neck, trunk, hips, and knees maximally for rapid somersaulting body rotation); and (c) high body CM at touchdown on the mat (by releasing the knees and extending the hips above the top level of the horse to display ‘form’ for bonus points, and simultaneously to prepare for controlled landing). Acknowledgement: The International Olympic Committee funded this study.Keyword(s): athletics/sports, olympic related, technique