Chiral Symmetry has played a fundamental role in particle physics and is
still a major theoretical tool. In this Lecture, I shall describe how
Bruno Touschek first introduced it in 1957, after the discovery of the
non-conservation of Parity. Further theoretical developments, by Salam,
Feynman and Gell-Mann , will be described. Some recent applications, to
obtain fundamental hadronic quantities like the pion scattering lengths,
will be illustrated in detail.