  A model independent formalism for the electron positron annihilation reaction
$e^++e^-\to a_1(1260)+\pi $ has been derived. The differential and total cross
sections and the elements of the spin--density matrix of the $a_1$-meson were
calculated in terms of the electromagnetic form factors of the corresponding
$\gamma^*a_1\pi $ current. Simple models of $a_1$ form factors have been fitted
to the available cross section data and they allow to give numerical
predictions for the different observables.
