We had the unique opportunity to study the effects of transdermal nicotine on markers of haemostasis and serum lipids in patients with ulcerative colitis; all were non-smokers and were given transdermal nicotine to assess its value in maintenance therapy for colitis. In a controlled double-blind trial, 45 patients with ulcerative colitis in remission on 5-aminosalicylic acid, were randomly allocated to receive transdermal nicotine (20) or placebo (25) patches. Markers of haemostasis, including platelet activation (platelet volume and surface expression of P selectin), endothelial damage (plasma von Willebrand factor antigen) and plasma fibrinogen were measured at the beginning and after 12 weeks of treatment. The white cell count and serum lipids were also measured. Nicotine significantly lowered plasma fibrinogen but did not affect markers of platelet activation, endothelial damage, white cell count and serum lipids. The possibility that transdermal nicotine may beneficially influence cardiovascular risk factors warrants further exploration.