Fast-acting insulin aspart (faster aspart) is insulin aspart (IAsp) with two added excipients, L-arginine and niacinamide, to ensure formulation stability with accelerated initial absorption after subcutaneous administration compared with previously developed rapid-acting insulins. The pharmacokinetic/pharmacodynamic properties of faster aspart have been characterised in clinical pharmacology trials with comparable overall methodology. In subjects with type 1 (T1D) or type 2 (T2D) diabetes, the serum IAsp concentration-time and glucose-lowering effect profiles are left-shifted for faster aspart compared with IAsp. In addition, faster aspart provides earlier onset, doubling of initial exposure, and an up to 2.5-fold increase in initial glucose-lowering effect within 30 min of subcutaneous injection, as well as earlier offset of exposure and effect. Similar results have been shown using continuous subcutaneous insulin infusion (CSII). The improved pharmacological properties of faster aspart versus IAsp are consistent across populations, i.e. in the elderly, children, adolescents and the Japanese. Thus, the faster aspart pharmacological characteristics more closely resemble the mealtime insulin secretion in healthy individuals, giving faster aspart the potential to further improve postprandial glucose control in subjects with diabetes. Indeed, change from baseline in 1-h postprandial glucose increment is in favour of faster aspart versus IAsp when used as basal-bolus or CSII treatment in phase III trials in subjects with T1D or T2D. This review summarises the currently published results from clinical pharmacology trials with faster aspart and discusses the potential clinical benefits of faster aspart compared with previous rapid-acting insulin products.