Abstract This chapter explains what tracing is. Differing descriptions of the expression are discussed. Tracing does not seek to examine intention; tracing imposes a proprietary interest. The chapter discusses the principles of tracing at common law and how a person becomes a legal owner of a substitute asset. In particular, the rules as to indentification of a substitute asset are discussed. The chapter contains a detailed discussion of the case law on tracing at common law. Attempts to distinguish tracing from ‘following’ are discussed. The chapter distinguishes tracing against the wrongdoer from tracing against a third party.