This report identifies the most vulnerable workers, i.e. those in employment situations characterised by multiple disadvantageous conditions, such as involuntary part-time work combined with very few working hours. Drawing on indicators from the EU Labour Force Survey and the European Working Conditions Survey, the report highlights the groups most likely to be engaged in such forms of employment and describes recent trends in their labour market participation. The report also examines the working conditions and overall job quality of these workers. It provides an overview of relevant policy and legislative developments aimed at reducing vulnerability and supporting transitions towards more secure and sustainable forms of employment.