This chapter provides new evidence on the incidence of non-regular employment, defined as all types of employment that do not benefit from the same degree of protection against contract termination as permanent employees, and its impact on labour market duality and inequalities in job security across workers. In most OECD countries, regulations concerning termination of non-regular contracts are typically less costly for employers and less protective for workers than those applying to the dismissal of permanent employees. These differences in legislation are reflected in both actual and perceived job security. Moreover, there are growing concerns that large differences in regulations across contracts tend to concentrate any required labour market adjustments on non-regular workers, thereby increasing labour market segmentation. Policy options to reduce this labour market divide include making the use of temporary contracts more difficult and costly, relaxing regulations on dismissal of permanent workers or fostering convergence of termination costs across contracts, including by introducing a single or unified contract. Each of these options involves overcoming implementation difficulties and requires complementary reforms to be effective.