In recent decades, economic policy makers across Europe have sought to increase labour market flexibility by promoting the use of temporary employment. The articles in this Feature provide new results on how fixed-term and agency work contracts affect firm productivity and how the segments of two-tier labour markets interact. This article points to a possible trade-off between efficiency and equity when deregulating labour markets. Taken together, the evidence presented in this Feature suggests that flexible forms of employment can be both a boon and a bane for labour markets and for society as a whole.