The purpose of this study is to determine the impact of tetrahydrocannabinol (THC) administration on motivational, subjective, and physiological effects of electronic cigarettes. The study's goals are to test demand for e-cigarettes, tobacco craving, affect, heart rate, blood pressure, expired breath carbon monoxide, and cognitive performance. Researchers will compare multiple doses of THC and a placebo in participants who smoke e-cigarettes and either smoke or vape THC in the laboratory.