The development and validation of survey measures for electronic nicotine and non-nicotine delivery system (ENDS) use has not kept pace with the burgeoning research on them. This, along with the diverse and evolving nature of ENDS, presents several unique measurement challenges and hampers surveillance and tobacco regulatory research efforts. In this commentary, we identify four important areas related to ENDS use (describing ENDS products; defining current use; evaluating frequency and quantity of use; and characterizing devices and e-liquids) and summarize a selective review of the measurement and definitions of these constructs across prominent national tobacco use surveys and 30 projects within the 14 federally-funded Tobacco Centers of Regulatory Science. Across these national, regional, and local studies, there was considerable variability and relatively little consensus in ENDS use measures - thus highlighting the need for caution when comparing findings across studies or over time until more research is available to evaluate the sensitivity of findings to differing measures. Drawing from the nascent ENDS use measurement research literature and our experiences, we conclude with general considerations for measuring ENDS use for tobacco researchers as an initial step towards the development of consensus measures.