  We explore the occurrence of pairing effects above $T_{\rm c}$ in the 2D
attractive Hubbard model. The presence of pairs above $T_{\rm c}$ goes beyond
the BCS approximation, in which pair formation and condensation occur at the
same temperature. Using the fully self-conserving $T$-matrix formalism, which
is valid above $T_{\rm c}$, we find that (1) the distribution function, $n(k)$,
shows a 10\% change of the weight from ``below'' to ``above'' $k_{\rm F}$ with
respect to the free case, and (2) the phase shift, $\delta\phi(\omega,k)$,
shows $\Theta$-like behavior as a function of $\omega$ for large momentum $k$
along the diagonal of the Brillouin zone. Our calculations have been carried
out for an interaction of $U/t = - 4.0$ and a temperature of $T/t = 0.125$,
where $t$ is the hopping matrix element between nearest neighbors. We conclude
that for such an interaction value the Fermi surface is not a well-defined
quantity.
