The adsorption of Rhodamine 6G (R6G) in aqueous suspensions of Wyoming montmorillonite (WyM) is investigated by electronic absorption and emission spectroscopies. The loading range studied is between 0.1% and 100% of the cation exchange capacity. The monomer of Rhodamine 6G can be adsorbed on the external and on the internal surfaces of the clay. Experimental results show that the increase of stirring time favors the monomer migration from the external to the internal surface on a time scale of days, mainly for low relative dye/clay concentrations. The metachromatic effect observed for the R6G/WyM system is attributed to the dye aggregation, which depends not only on the relative dye/clay concentration but also on the dispersion degree of the clay suspension.