Rationale: Several previous investigations with animals and humans have suggested that nicotine enhances prepulse inhibition of the startle reflex (PPI). However, the administration of nicotine activates mesolimbic dopamine, and activation of mesolimbic dopamine is known to attenuate prepulse inhibition of the startle reflex (PPI), which might suggest that nicotine would decrease PPI. Objective: The primary aim of this study was to test rigorously the effects of smoking high nicotine cigarettes on PPI and other measures (e.g., heart rate, craving, and mood) when the concentration of nicotine peaks in the brain (i.e., immediately after smoking). Methods: Thirty smokers participated in two experimental sessions 1 week apart. Two high nicotine cigarettes were smoked in one session, and two control cigarettes were smoked in the other session after overnight deprivation. Results: The results indicated that smoking the high nicotine cigarettes decreased PPI and that PPI increased across trials in both conditions. The interaction between nicotine dose and trial was not significant, although it appeared that high nicotine may have reversed an increase in PPI across trials in the control condition. High nicotine cigarettes also significantly increased heart rate, decreased the latency to peak startle response on control trials, but did not alter the magnitude of the startle response. Discussion: The findings suggest that either high nicotine cigarettes reduced PPI, or possibly, that high nicotine cigarettes may have reversed an increase in PPI across trials as evident in the control condition.