Micronutrients are substances with numerous functions, contributing to body metabolism, immune and oxidative defence, and signaling processes. Therefore, the compensation of micronutrients deficiencies is obviously essential in critically ill patients. While patients feeding orally or enterally might not need additional micronutrients, patients receiving parenteral nutrition and micronutrient-deficient patients, such as malnourished patients, patients with prolonged ICU stay or patients losing micronutrients, will require adequate supplementation of trace elements, vitamins and perhaps other pharmaconutrients. This chapter discusses the influence of micronutrients on inflammatory reactions and lists the most important pharmaconutrients, their functions, whereas actual and current recommendations are given elsewhere. Selected pharmaconutrients will be briefly discussed within the context of the recent literature.