  Deviations of the decay law from exponents are discussing for a long time,
however, experimental proofs of such deviations are absent. Here in the general
form is shown that the conclusions about non-exponential contributions are due
to the disregarding of advanced interactions, i.e. at principally
non-relativistic considerations. We consider decay processes in the frame of
interactions duration of the quantum field theory. We show that at this basis
the usual exponential decay has place.
