The paper arises from new developments which have taken place in the labour market, namely the emergence and spread of new working patterns and the introduction of social security pro-visions geared to increase labour mobility. On one hand, the changes which labour law is undergoing unravel a tension towards the creation of employment through the establishment of working patterns able to suit labour demand. On the other hand, social se-curity is turning into an instrument directing manpower towards different jobs, developing sectors of the economy, and new work-ing patterns. In other words, we are going to experience a blur-ring of the borderlines between social security and labour law. In this context, the definition of the terms of the interaction between the two systems becomes of overwhelming importance.