The dihedral angle theta of I,1'-binaphthyl derivatives is quantitatively related to the wavelength splitting Delta lambda(max) of the 220 nm couplet of the CD spectra. This relation is almost independent of measurement conditions (solvent, concentration). Its reliability has been quite successfully tested on about 10 compounds derived from 2,2'-dimethyl-1,1'-binaphthyl. A simple and versatile method for the conformational assessment of this class of compounds is reported.