  Photoproduction of two pions on nucleon and deuteron is studied for photon
energies from threshold up to $E_\gamma = 1.5$ GeV. For the elementary operator
an effective Lagrangean approach is used with resonance and Born contributions.
The model parameters are fixed by resonance decay widths and multipole analyses
of single pion photoproduction. A satisfactory description of total cross
sections of two-pion production on the proton for various charge channels is
achieved, except for $\pi^0\pi^0$ production for which a significant
underestimation is found near threshold. The operator then serves for the
evaluation of this reaction on the deuteron in the impulse approximation. In
addition, $NN$ rescattering in the final state is taken into account, but $\pi
N$ and $\pi\pi$ rescatterings are neglected. Results are presented for total
cross sections and target asymmetries.
