The optical rotatory dispersion curves of some l-substituted (including 1-benzyl) tetrahydroisoquinolines have been measured. The curves for an extensive series of bisbenzyltetrahydroisoquinoline alkaloids of different structural and stereochemical types with two diphenyl ether linkages have also been measured and related to the stereochemistry and to the ultraviolet absorption of the compounds. In this Paper we present the results obtained from rotatory dispersion measurements on a series of bisbenzylisoquinoline alkaloids and some related simple l-alkyl- and l-benzylisoquinolines of known absolute configuration. Our present theoretical knowledge permits us to offer only empirical correlation between dispersion curves and configuration for compounds of known structure, but these may help in allotting configurations to newly discovered compounds.