The Échelle de mesure de la force de motivation pour les études médicales (French version of Strength of Motivation for Medical Studies [SMMS]) includes 16 items, and its short version, 15 items (SMMS-R). Both versions have been the subject of structural analyses in Netherlands and France. However, these previous works presented several methodological weaknesses. This study has involved 410 second- and third-year medical students. Based on a rigorous methodology, it concerns the structural properties of the scale, measurement invariance and gender differences. A polychoric correlation matrix were submitted to exploratory and confirmatory factor analyses using mean and variance adjusted diagonally weighted least squares method for estimation. Measurement invariance was carried out by multi-group confirmatory factor analysis. Gender differences were explored statistically. The results validate a new three-factor structural model (acceptance of sacrifices, tenacity, commitment) for the French version of the scale. Measurement invariance testing shows that the item/factor interaction is not influenced by gender. Finally, data analysis strengthens that the motivational force is similarly expressed by female and male students.