IntroductionAlcohol hangover is a common phenomenon, experienced by numerous people amongst alcohol consuming societies. Recent research has demonstrated the impact of this phenomenon on various aspects such as quality of life, cognitive functioning and affect, work effectiveness and economy [1]. Nevertheless, so far, no measure was found to be effective in reducing the burden of hangover, besides alcohol abstinence. While several strategies and products were systematically evaluated, none of them was found efficient [2].Two of the most purchasable drugs, alcohol and tobacco, are often co-abused. In fact, about 7% of the U.S. population is co-dependent [3,4]. Additionally, alcoholism is estimated to be 10 times more common amongst smokers than nonsmokers [5]. Concurrent use of these drugs poses significant public health concern and a large financial burden upon society.Results from animal and human studies have demonstrated multiple mechanisms for alcohol and nicotine co-use. Smokers reported that they felt less intoxicated compared with nonsmokers after the administration of an identical dose of alcohol [6]. These findings suggest that smokers are more tolerant to alcohol's effects. In rodents, co-treatment may be influenced by each drug more effectively than the adverse effects of the both [7]. Supporting this concept, neuroimaging studies, which had been conducted on people during alcohol withdrawal period with continuity of cigarette smoking, found decreased severity of the withdrawal-related changes in gamma-aminobutyric acid (GABA) neurotransmitter activity [8].Considering these interactions found, it is surprising that several nonscientific internet sites such as, WikiHow, HubPages and HowToPrevent.com, which are full of good advice on preventing a hangover after a night of excessive drinking (lowering alcohol consumption, eating before drinking or avoid dehydration) recommend avoiding smoking, including passive exposure to cigarette smoke during a drinking night in order to reduce hangover symptoms. (http://www. wikihow.com/Prevent-a-Hangover; http://kennywordsmith.hubpages. com/hub/How-To-Get-Over-A-Hang-Over---Best-HangoverRemedies;http://www.howtoprevent.com/physical-health/how-toprevent-a-hangover/). This popular concept, that avoiding smoking can ameliorate hangover symptoms is currently not supported by the medical literature. In order to evaluate whether this concept is valid, we conducted a study which compares the tendency to develop hangover symptoms between smokers and non-smokers. Materials and Methods Participants739 University students were recruited in this observational, crosssectional study, during September and October of 2009. 252 subjects have met the exclusion criteria, 47 due to chronic headache or head trauma, 124 due to alcohol abstinence and 81 participants who have not Abstract Background: The popular concept which claims avoiding smoking contributes to meliorate hangover symptoms is currently not supported by the medical literature. In order to evaluate whether this concept is ...