  We study multiparticle production in the unbroken $(3+1)$-dimensional
$\lambda\phi^4$ theory using the semiclassical method of singular solutions. We
show that the probabilities of these processes are exponentially suppressed in
terms of a small coupling constant $\lambda \ll 1$ if the multiplicity of the
final state is large: $n \gg 1$. At $ n \ll \lambda^{-1}$ the probabilities
agree with well-known perturbative results. At $ n \gg \lambda^{-1}$ they are
dominated by loop effects and decrease exponentially with $n$, as we show for
the first time.
