The Raman spectrum of all-trans anhydrovitamin A in hexane at 77 degrees K is presented. The similarity of the Raman spectra of anhydrovitamin A and the protonated Schiff base of retinal is striking. The implications of this for visual pigment studies and bacteriorhodopsin are discussed. Tentative assignments of geometry for four cis-trans isomers of anhydrovitamin A are made on the basis of the observed room-temperature absorption spectra.