This Library Note provides a chronology of key developments in the reform of the House of Lords since 1900. It does not provide a comprehensive account of all reform proposals, but briefly summarises the context and outcome of significant proposals for reform of the composition and powers of the House in order to illustrate the shifting debate on the Lords over the last century. More detailed chronologies of recent reform proposals may be found in House of Lords Library Notes ‘Proposals for Reform of the Composition and Powers of the House of Lords, 1968–1998’ (July 1998, LLN 98/004) and ‘House of Lords Reform 1997–2010: A Chronology’ (June 2010, LLN 2010/015).