Experimental research on electronic cigarettes (e-cigarettes) is sparse. Regulated as tobacco products by the US Food and Drug Administration, e-cigarette safety has not been determined. This enables the sale of e-cigarettes and tobacco-derived nicotine solution to consumers without rigorous safety regulations that would be required if the products were regulated as drug delivery devices.1 As such, despite the recent popularity of e-cigarettes as an alternative to cigarette smoking, consumers currently do not have industry-regulated information on the concentration of e-cigarette solutions or their safety.1 The present study reports the nicotine concentration of several of these solutions.