The use of plasma for various medical applications, i.e., so-called “plasma medicine”, is gaining increasing interest, e.g., for sterilisation and decontamination purposes, for wound healing, the treatment of skin diseases, dental cavities, etc. In recent years, a lot of attention goes to cancer treatment, where promising results have been obtained already, both in vitro and in vivo. Plasma appears to be able to attack a wide variety of cancer cells, without damaging healthy cells. One of the most commonly used plasma sources for this purpose in a plasma jet. We have studied in detail the chemistry in an argon plasma jet expanding in humid air, by means of 0D chemical kinetics modelling, to elucidate which are the important species formed in the plasma jet, important for biomedical applications, i.e., mainly reactive oxygen species (ROS) and reactive nitrogen species (RNS). We have also studied the interaction of ROS with bacterial cell wall components to better understand the atomic-scale mechanisms of bacteria killing (for plasma-based sterilisation, but also for wound treatment, dental treatment, etc). Currently we are mainly focussing on plasma for cancer treatment, studying the interaction of ROS (and RNS) with various components in human cells, like DNA, proteins, and especially phospholipids in the plasma membrane of cells, to understand whether and how ROS (and RNS) can penetrate through the membrane and enter the cell, and/or give rise to phospholipid (per)oxidation and pore formation in the membrane. We also study the plasma interaction with liquid medium, important for real applications. Last but not least, we are also doing experiments on plasma treatment of various types of cancer cells, including both direct treatment and indirect treatment by plasma activated medium, in collaboration with the groups PPES (S. Dewilde, Biomedical Sciences) and CORE (E. Smits, Oncology, Faculty of Medicine and Health Care).