The magnetic flux tubes that rise across the convection zone to produce active regions are shown to develop a difference in inclination between their preceding and follower sides. This asymmetry is such that the following wing is more vertical (i.e., closer to the radial direction) than the preceding side. An asymmetry of this kind can be obtained as a natural consequence of the conservation of angular momentum along the rise. This process may explain a number of the observed asymmetries in morphology and behavior of the preceding and follower parts of the active regions. We present results of numerical simulations showing this effect and discuss possible observational consequences.