  The present status of theoretical and experimental investigations of the
decay rate of a positronium is considered. The increasing interest to this
problem has been caused by the disagreement of the calculated value of
$\Gamma_3 (o-Ps)$ and the recent series of precise experiments. The necessity
of new calculations on the basis of the quantum field methods in bound state
theory is pointed out with taking into account the dependence of the
interaction kernel on relative energies.
