The disposition kinetics of nicotine and cotinine enantiomers was determined in rabbits. The clearance of (R)-nicotine was similar to that of (S)-nicotine, but clearance of (R)-cotinine was twice that of (S)-cotinine. Fractional conversions of both enantiomers of nicotine to cotinine were approximately 50%. These results suggest that in rabbits the biotransformation pathways of cotinine, but not nicotine, are influenced by stereochemistry. The disposition kinetics of nicotine enantiomers in beagle dogs was also studied. In dogs, the clearance of (R)-nicotine was slightly greater than the clearance of (S)-nicotine. Methods for the synthesis of (R)-nicotine and (R)-cotinine of high enantiomeric purity and a gas chromatographic method for determination of nicotine enantiomeric purity are described.