Many methods have been proposed for the prediction of LogBB . Some of these methods are qualitative methods and attempt to distinguish BBB permeable drugs from those that are not permeable . Others, provide a quantitative estimate of the BBB permeability or a score that correlates with BBB permeability . A quantitative estimate was deemed to be more suitable for incorporation into the workflow for an evolutionary algorithm. The available methods have significant differences in the prediction accuracy and in the time requirements for the prediction.