The Underwater Vision Profiler 5 was developed at the Laboratoire d’Océanographie de Villefranche-sur-Mer (LOV) to provide consistent measurements of particle abundance and size. Using the standard settings, the UVP5 images a volume of about 1 L at a frequency of 6 to 20 Hz and can be deployed down to 6000 m depth. Particles on each image are automatically sized. Further data processing of all particles allows for the calculation of the particle size distribution – the particle abundance or biovolume in increasing size intervals. The UVP5 STD version covers the size range from 102 μm to ∼ 50 mm ESD (where ESD denotes the equivalent spherical diameter), whereas the HD version covers the size range from 64 μm to ∼ 50 mm ESD. Inter-calibrated UVP5 units are globally in use by several teams. As the UVP5 is mostly integrated in the CTD (conductivity, temperature and depth) rosette and has its own pressure sensor, the fine-scale vertical distribution of particles and major plankton groups can be related to environmental data obtained with other sensors mounted on the CTD rosette.