According to the National Comorbidity Survey, in the U.S., 1 in 7 individuals 15-54 years old had a history of alcohol dependence, and 1 in 4 of nicotine dependence (Anthony et al., 1994). Alone, and in combination, these drugs produce a variety of effects on physiology, subjective experience, emotion and cognition that affect behaviour and appear to be important determinants of both the initiation and patterns of their use. The cognitive effects of these two substances, the focus of this paper, are so varied that generalizations about them are difficult to impossible. A plethora of factors, including the environment, the cognitive task, the individual subject, as well as the time, route and rate of drug administration, all are important alone and in concert in determining possible drug effects. For example, with alcohol, factors such as the time since consumption (Westrick et al., 1988), gender, specific task, and the effects of the ascending vs. descending limb of the blood-alcohol curve are important mediating factors on cognitive performance (De Wit et ai., 1990; Niaura et al., 1987). The picture is further complicated by the potential interaction between drugs. For example, the high correlation between alcohol and nicotine use, that is, people who drink also tend to smoke, and vice versa demands for ecological validity that the effects of both drugs individually and interactively be considered. A common current belief is that nicotine's effect on cognition is opposite to that of alcohol. This position provides a strong impetus for studying the combined effects of these two drugs on cognition. Caffeine is also thought by many to be a 'cure' for the debilitating effects of alcohol and thus the study of the combined effects of caffeine and alcohol on cognitive abilities is also warranted.