Current evidence about the therapeutic potential of nicotine is strongest for ulcerative colitis. The role, if any, of nicotine therapy in Parkinson's or Alzheimer's diseases is not clear, but further research appears warranted. We need more information about the tolerability and safety of nicotine administration in such diseases. At present, any therapeutic trials of nicotine therapy should occur only as part of research protocols. Further nonjudgmental examination of the perceived effects of tobacco use may lead to other uses of nicotine. However, given the widespread morbidity and mortality directly attributable to tobacco use, no form of tobacco should be used to deliver nicotine. We encourage everyone who uses tobacco products to quit.