The eruption of magnetic flux tubes from the overshoot layer due to instability and the dynamics of their subsequent rise through the solar convection zone are followed by numerical simulation. Special emphasis is put on the possibility of explaining observed regularities of the active regions at the surface (tilt angles, latitude of emergence, asymmetry between preceding and following parts, etc). Instability sets in with non-axisymmetric (undular) modes at azimuthal wavenumbers $m=1$ and $m=2$ if the field strength exceeds values of the order of $10^5$ G. At the same time, such strong initial fields are required to reproduce the observable properties of sunspots and active regions. Consequently, a consistent picture of storage, instability and eruption of solar magnetic fields emerges.