Aim To observe the effect of cigarette smoking on level of serum soluble intercellular adhesion molecule-1 (sICAM-1) and cerebral hemodynamic changes in transient ischemic attack (TIA) patients in order to investigate the mechanisms of cerebral thrombosis. Methods The level of serum sICAM-1 was determined by two-layer antibody sandwich enzyme-linked immunosorbent assay (ELISA) in 31 cases of smokers with TIA, 25 cases of non-smokers with TIA, 26 healthy smokers, 28 healthy non-smokers; The cerebral hemodynamic changes were assessed by measuring blood flow velocity in bilateral large arteries with transcranial Doppler (TCD). Results The level of serum sICAM-1 in cases of smokers with TIA was higher than that of non-smokers with TIA (p<0.05) and was much higher than that of healthy non-smokers (p<0.01); The level in healthy smokers was higher than that of healthy non-smokers (p<0.05); The levels in severe smokers and moderate smokers were higher that of mild smokers and healthy non-smokers (p<0.01 and p<0.05); The level of serum sICAM-1 was well correlated with smoking index (r=0.428, p<0.01); The blood flow velocity in bilateral middle cerebral artery (MCA) increased compared with that of before smoking a cigarette (p<0.05). Conclusions Cigarette smoking increased the level of serum sICAM-1 in TIA patients, healthy smokers and the blood flow velocity in MCA.