Non-steroidal anti-inflammatory drugs (NSAID) are used to alleviate clinical inflammatory symptoms (e.g. pain, swelling and reduced function). Leukocytes, upon activation during inflammatory states, generate radical oxygen species (ROS) which primarily are intended for host defence against invading pathogens. Certain NSAID can modify the generation of ROS from stimulated neutrophils ranging form increased production to reduced production. Preliminary experiments in our laboratory have shown that different NSAIDs have opposing effects on the ability of leukocytes (granulocytes and monocytes) to produce ROS upon a standardized stimulus, i.e. phorbol myristate acetate (PMA). Paracetamol has a marked inhibitory effect and ibuprofen has a facilitating effect on ROS production. An inhibitory effect of paracetamol was also seen when examining platelet activation markers, whereas acetylsalicylic acid showed a clear enhancing effect in this respect. We want to examine if intake of paracetamol or ibuprofen in vivo have similar effects on leukocyte ROS production and platelet activation, respectively.