The success of the biorefinery will depend on deriving value from the lignin fraction of lignocellulosic feedstocks. Thus, it will be necessary to develop procedures that provide a separate and usable lignin stream for chemical transformation. A wide range of processes have been developed that afford isolated lignin, but very few of these methods are practical for the biorefinery, as they target lignin analysis or lignin removal, and are largely impractical for large scale use or introduce severe structural changes in the lignin that significantly reduces its potential as a chemical feedstock. This chapter will introduce several methods that isolate lignin for analytical purposes, or for its removal from lignocellulose. The majority of the chapter then discusses processes for biomass fractionation - methodology that gives lignin streams in high yield and purity, and which offer potential utility within the biorefinery.