The influence of a strong magnetic field (up to 12 T), parallel to the Si‐SiO2 interface on the injection of hot electrons from Si into SiO2, has been measured in the case where the heating electric field is uniform and normal to the interface. The experimental results show that the influence of the magnetic field can be either an increase or a decrease of the injection probability depending on the type of test device used. These results are compared to a numerical simulation based on the hypothesis that injected electrons are in majority ballistic (‘‘lucky’’) electrons. It is shown that a possible interpretation of the experimental results can be found with this model by taking into account the influence of interface roughness on the escape conditions of hot electrons. Numerical results based on a simple model are given that show for the first time that interface roughness may be an important factor to consider in the study of hot‐electron injection physics.