  The study of the transition between galactic and extragalactic cosmic rays
can shed more light on the end of the Galactic cosmic rays spectrum and the
beginning of the extragalactic one. Three models of transition are discussed:
ankle, dip and mixed composition models. All these models describe the
transition as an intersection of a steep galactic component with a flat
extragalactic one. Severe bounds on these models are provided by the Standard
Model of Galactic Cosmic Rays according to which the maximum acceleration
energy for Iron nuclei is of the order of $E_{\rm Fe}^{\rm max} \approx 1\times
10^{17}$ eV. In the ankle model the transition is assumed at the ankle, a flat
feature in the all particle spectrum which observationally starts at energy
$E_a \sim (3 - 4)\times 10^{18}$ eV. This model needs a new high energy
galactic component with maximum energy about two orders of magnitude above that
of the Standard Model. The origin of such component is discussed. As
observations are concerned there are two signatures of the transition: change
of energy spectra and mass composition. In all models a heavy galactic
component is changed at the transition to a lighter or proton component.
