The object of this paper is to point out that the hypothesis of decaying states,*i.e.*, states with amplitude having a factor e^{γt} (*γ*-real) is not compatible with the wave equation with a hermitian hamiltonian. An attempt has been made to obtain the expression for relative population density in general. It is shown that the usual expressions for the transition rates, which are proportional to time, may be obtained for a very restricted interval of time.