Abstract: This study is concerned with the heat transfer and aerodynamics of a needle-free epidermal powdered delivery system (biolistic system). Numerical simulations of a transient impinging jet being issued from a biolistic device have been performed to study momentum and heat transfer characteristics, with an emphasis on the gas properties immediately above a skin target. It is found that during the operation the impingement heat transfer is very unsteady. The starting process dominates features of the flow and heat transfer as it approaches the skin target. The effects of this impinging jet on the human skin are subsequently explored by a one-dimensional convection heat transfer model. Spatial-temporal characteristics of skin heat transfer are analysed and demonstrated the temperature fluctuations in the epidermal layer of skin are negligible (<1 °C). These quantitative results indicate the biolistic system is patient-friendly and pain-free, apart from the unique epidermal vaccination capability.