Résumé : The main objective of this paper is to analyze the problem of population ageing in terms of the cessation of professional activity (and especially premature labour market withdrawals) in order to provide the various public and private administrations active in these fields with some food for thought. Results show that employer-driven obligation to stop working (owing to business closure, redundancy, dismissal, early retirement, etc.), marital status (married/widowed) and health status are the main reasons for the premature cessation of activity common to all four countries studied (Belgium, Finland, the Netherlands and the United Kingdom), while the desire to retire from the labour market or live off private wealth (voluntary cessation) has a significant effect only for Belgium and the Netherlands. However, the impact of this reason on the retirement age is much lower than that of departure enforced by the employer (2 to 3 times lower in these two countries).