Nicotine flux, the rate of electronic nicotine delivery system (ENDS) nicotine emission, is important in determining ENDS abuse liability. However, flux does not account for user behavior, including puff duration. Along with nicotine flux, puff duration limits the dose of nicotine that can be inhaled. Controlling both flux and puff duration allows regulators to constrain nicotine dose effectively. This study examined the effects of differing ENDS nicotine fluxes (by manipulating liquid nicotine concentration and holding device power constant), with user puff duration limited to 2 s. Participants (N = 32) completed four sessions, each session differing by nicotine flux (no flux, low flux, cigarettelike flux, and high flux conditions). Participants completed two ENDS use bouts in each session while puff duration was limited to 2 s. Plasma nicotine concentration, heart rate, and subjective effects were measured. At higher flux, higher plasma nicotine concentration and higher heart rate were observed. Moreover, higher fluxes decreased ratings of craving and urge to use nicotine and increased positive subjective effects, such as calmness. This study demonstrates that by manipulating nicotine flux and limiting puff duration, nicotine dose can be controlled. Subsequent research should demonstrate the effects of manipulating puff duration systematically. Results underscore the importance of targeting both flux and puff duration for ENDS regulation, intended to reduce abuse liability while maintaining the potential to facilitate transitions from cigarettes to ENDS. (PsycInfo Database Record (c) 2024 APA, all rights reserved).