There are many clinical scoring systems to provide an assessment of levels of sedation, and commonly used ones include Ramsay and Bloomsbury scales. The other assessment tools are electroencephalograms, bispectral index, and auditory evoked potentials. It takes four half-lives of a drug given by intravenous infusion to achieve steady state. It is therefore necessary to start with a loading dose to minimize delays to achieve adequate sedation. The side effects of sedatives, ideal properties of sedatives, and commonly used sedatives are discussed in this chapter. The chapter reviews intravenous anaesthetic agents, volatile anaesthetic agents, benzodiazepines, opioids, alpha-2 receptor agonists, neuroleptic agents, neuromuscular blockade, and use of protocols and sedation breaks. The recent Awakening and Breathing Control (ABC) trial suggested that a 'wake up and breathe' protocol that pairs daily spontaneous awakening trials with daily spontaneous breathing trials results in better outcomes for mechanically ventilated patients in intensive care.