The acquisition and maintenance of chronic nicotine (Nic) self-administration (SA). Adult male Sprague-Dawley rats acquired Nic self-administration (30 μg/kg/injection, iv) without prior training, priming or food deprivation. Nicotine was available 23 hours/day for 12-15 days; self-administration terminated on the 15th day with a microinjection experiment. Rats self-administering nicotine had significantly more active than inactive lever presses [two way ANOVA: time, p < 0.001; SA (active vs. inactive) p < 0.001; time × SA, p < 0.001] and more active presses than the saline (Sal) SA group (two way ANOVA: time, p < 0.001; SA group, p < 0.001; time × SA group, p < 0.001). Active and inactive presses were not different in the Sal SA group [time, p > 0.05, SA (active vs. inactive; p > 0.05). All data are expressed as mean ± SEM.