The optical characteristics of resonant locally isotropic but inhomoge
neous media are analyzed. Computations were based on the Maxwell-Bloch
equations allowing for medium inhomogeneity. The main result of the c
omputations is that the integral optical characteristics of the medium
volume can depend on the direction of the optical pulse propagation.
In particular, the medium transmittance is changed when this direction
is reversed. An explanation of this phenomenon is also given.