The effect of finiteness of the ion-Larmor radius on the Rayleigh-Taylor instability of a rotating plasma of variable density is studied in this paper. A semi-finite plasma in which density is assumed to be stratified one-dimensionally, in a direction transverse to that of the static uniform magnetic field, is considered. The inclusion of the finite-Larmor-radius (F.L.R.) effect is found to have a stabilizing influence on the unstable configuration.