AbstractA new twisted smectic mesophase formed in Tween 80 (1) (monooleate of the ether of sorbitan with 4 mol of polyethyleneglycol)‐water system was found. The induced circular dichroism (CD) spectra of achiral molecules dissolved in this twisted smectic mesophase are compared with those in the thermotropic cholesteric mesophase. Pyrene and fluorene and their derivatives, acridine, phenazine, and phenothiazine were used as achiral molecules (solute molecules). It was found that the signs and shape of the induced CD bands observed in the twisted smectic mesophase were dependent on the solute concentration. The magnitude of the induced CD bands was dependent on the symmetry of the solute molecules and the value of the geometrical ratio of short‐axis to long‐axis of the solute molecules. Furthermore, it was demonstrated that the relative polarization directions of the solute molecules could be determined by means of the induced CD in the Tween 80‐water system using a simple modified C2‐symm