Inclusion criteria:  Female and male smokers, aged 18 to 65 years veterans and non-veterans who have been smoking tobacco cigarettes for at least a year smoke ≥ 5 cigs/day ; urine cotinine levels > 100 ng/mL consistent with nicotine intake of an active smoker (23) not seeking treatment at the time of the study for nicotine dependence Good health as verified by medical history, screening examination, and screening laboratory tests For women, not pregnant as determined by pregnancy screening, nor breast feeding, and using acceptable birth control methods.  Exclusion criteria:  History of major medical or psychiatric disorders that the physician investigator deems as contraindicated for the subject to be in the study regular use of psychotropic medication (antidepressants, antipsychotics, or anxiolytics) current alcohol or substance dependence for any other recreational or prescription drugs other than nicotine use of e-cigarettes more than 10 days in the past 30 days urine drug screening indicating recent illicit drugs use (with the exception of marijuana).