  Using Monte Carlo simulations, finite-size effects of interfacial properties
in the rough phase of the Ising on a cubic lattice with $L\times L\times R$
sites are studied. In particular, magnetization profiles perpendicular to the
flat interface of size L$\times$R are studied, with $L$ being considerably
larger than $R$, in the (pre)critical temperature range. The resulting
$R$-dependences are compared with predictions of the standard capillary-wave
theory, in the Gaussian approximation, and with a field theory based on
effective string actions, for $L$=$\infty$.
