Osmotically active solutions, particularly mannitol, havebeen used for more than 30 years in the treatment ofintracranial hypertension. Recently hypertonic saline hasemerged as an alternative to mannitol. Both solutions areused worldwide, and their indications and long-term sideeffects are well known. More recently, knowledge abouttheir effects has increased, both limiting and expandingtheir clinical use. Here, we compare the systemic andcerebral effects of mannitol and hypertonic saline, as well astheir side effects and complications. Finally, we makerecommendations about their clinical use.