E-cigarettes are battery-powered electronic devices from which users can inhale nicotine following its aerosolisation from a heated liquid solution. Some regulators and public health bodies consider e-cigarettes as potentially playing a major role in tobacco harm reduction. The ability of e-cigarettes to deliver nicotine to smokers in a manner and form generally similar to cigarette smoking have been recognised as key factors in helping smokers reduce or cease the use of combustible cigarettes. Nicotine pharmacokinetic studies of e-cigarettes have been performed for several years and are beginning to show how nicotine delivery is evolving as the products themselves evolve. In this presentation, we provide a critical overview of the literature to describe what is known about nicotine delivery from e-cigarettes, by both presenting data from our own clinical studies and from what has been published in the literature. We will discuss how the progression of e-cigarette design, development, and user familiarity and subsequent use behaviour has allowed increases in nicotine delivery, in the context of how much and how rapidly nicotine is delivered during acute-use periods. This presentation will also provide insight into current research gaps, and highlight a potential need for standardisation of the methodologies used to assess nicotine uptake to facilitate comparisons between different products and between different sub-categories of e-cigarettes.