We examine the dependence of the native bacteriorhodopsin (bR) photocycle on ethanol, a solvent thought to perturb lipid structure, and monitor protein and chromophore absorption changes using time-resolved Fourier transform infrared (FTIR) spectroscopy. Ethanol treated samples under two pH conditions, 7 and 8. and two temperatures are examined. A faster M to N transition and slower N to O/bR transition are observed with 3 Methanol at pH 8. These rates are determined by monitoring several different infrared bands associated with the bR proton pump. An examination of the positions of the infrared bands associated with Asp85 and Asp96 (crucial bR proton transport amino acids) indicates that ethanol produces no obvious differences attributable to bR protein structural changes. Lipid-specific infrared bands in the CH stretching region and methylene region in the bR-lipid system and a model diphytanyl lipid undergo shifts in the presence of ethanol consistent with conformational changes in the lipid acyl chain. It also appears that bR protein infrared band,, not associated with the major proton pumping sites are shifted by the presence of ethanol; however, further studies are needed.