This chapter examines the differences between the more traditional groups of union members and the groups of employees who are relatively new to the labour force and the membership. It focuses on differences in satisfaction with and commitment to the union, two concepts that are central to the process of sustained union participation. The chapter also examines how successful Dutch trade unions have been in recruiting and retaining members from the groups of employees who are new to the labour force. It explores how the union density rate among traditional groups of employees compares to the union density rate among new groups of employees. The chapter utilizes data from a survey taken of Dutch union members to examine whether the more traditional groups of union members differ from groups of members that are relatively new to the membership. Several specific groups of employees are under-represented in the Dutch trade union movement.