“Flexibilisation”: the leitmotiv of contemporary employment is used by policy makers, employers, human resource managers, and the European money lenders. Part-time employment, limited-duration contracts, temporary work, freelancing, are only a few examples among the “new” forms of employment contracts. But what does this word actually mean in terms of employment and labour law? Using a comparative legal methodology with a focus on Swiss law, the study shows how flexibility challenges the three levels which, together, form the employment relationship: the law of the individual work contract (employment law), the law of collective bargaining (labour law), and social security law (in particular old-age and unemployment insurance). Inspired by the Decent Work principles of the International Labour Organisation, the book explores how the law can newly define the employment relationship and its contents. The study aims to grasp a definition of the new employment relationship and its contents, as well as to encourage more flexibility in social security systems as a counter-part to the flexibility in the individual employment relationship. The features of the “new” employment relationship thereby appear as possibly combining the wishes of flexibility and the social protection of the worker.