SBT is the most important predictor of weaning outcome, and other weaning or extubation predictors will not replace SBT. The main objective of other weaning and extubation predictors is to try to separate the group of patients who tolerate SBT and will be successfully extubated from those who tolerate SBT and will fail extubation, worsening the outcome of these patients. In this chapter, discussion will be focused on what a predictor is, its importance in health science and healthcare, and weaning predictors will be presented. There is a division between weaning predictors (when the failure group was composed of patients who failed SBT and extubation) and those that specifically predict SBT or extubation outcomes. Also presented are the individual parameters, characteristics, and signs that can predict weaning outcome, as well as the scores and indices. Extubation outcome was divided into airway-related and non-airway-related predictors. Future prediction scores should combine predictive factors for airway and non-airway failure in the same score, as different causes of failure need to be predicted by different factors. This will increase the predictive power of the scores. Furthermore, more important than creating new scores is the testing of existing scores in randomized and multicenter controlled trials.