Once analgesia is assured, sedation has special relevance in the critically ill ventilated patient's global treatment. Sedatives should be adjusted to individual needs, by administering minimal effective doses to achieve the AIM. This aim must be clearly identified, defined at the beginning of the treatment and revised on a regular basis, ideally at least once per shift. Sedation strategies should foresee the different needs throughout the day within dynamic sedation concept framework. Required sedation depth depends on the patient's psychological characteristics, foreseen evolution and patient tolerance to the support techniques used in treatment. Sedation monitoring permits identification and correction of under- or over-sedation, either of which could negatively influence critically ill patient evolution. The over-sedation concept must be applied to all situations where patients receive more sedation than required. This Spanish Society of Critical Care Medicine's Analgesia and Sedation Work Group recommends the Richmond Agitation Sedation Scale, due to its interrelationship with the Confusion Assessment Method Scale (CAM-ICU), for sedation monitoring in patients under light sedation while it recommends bispectral index sedation monitoring in patients under deep sedation. In the latter case, maintaining values under 40 on the bispectral index doesn't produce any benefits except in patients who require a maximum decrease in neuronal metabolism. To avoid recall phenomena, bispectral monitoring is highly advisable in patients treated with neuromuscular blockers.