INTRODUCTION: Electronic cigarettes (e-cigarettes) are gaining in popularity as an alternative to regular cigarettes, as they are viewed as potentially less harmful. However, it remains unclear how awareness about e-cigarettes is permeating through the general U.S. POPULATION: This study seeks to extend previous research and examine trends in e-cigarette awareness and perceived harmfulness, and their association with smoking-cessation efforts. METHODS: Data from three cycles (2012, 2013, and 2014) of the Health Information National Trends Survey were combined into a single data set. Controlling for survey year, multivariate logit models were used to determine the association between demographic characteristics and e-cigarette awareness, perceived harmfulness, quit attempts, and quit intentions. Data were analyzed in 2015. RESULTS: Awareness of e-cigarettes increased from 77.1% in 2012 to 94.3% in 2014. Controlling for demographic characteristics, e-cigarette awareness significantly increased in both 2013 and 2014, relative to 2012. Perception that e-cigarettes were less harmful than regular cigarettes declined from 50.7% in 2012 to 43.1% in 2014. Among smokers, no relationship was observed between e-cigarette awareness and past-year quit attempts or quit intentions, but those that viewed e-cigarettes as less harmful were less likely to have a past-year quit attempt. CONCLUSIONS: These analyses reveal a continued increase in overall public awareness of e-cigarettes and shifting harm perceptions relative to regular cigarettes. New regulatory oversight by the U.S. Food and Drug Administration may have major effects on both dimensions, which are worth continued monitoring.