We investigate the flow of a concentrated suspension through an abrupt, axisymmetric expansion, which can be encountered in such applications as materials processing or flow in the circulatory system. To date, few experimental data and modeling calculations are available for concentrated suspensions in expansion flow. In this study, suspensions of neutrally buoyant, noncolloidal spheres in Newtonian liquids undergo pressure-driven flow in an abrupt, axisymmetric 1:4 expansion. Particle concentration and velocity profiles are obtained by nuclear magnetic resonance imaging (NMRI). We aim to determine the influence of particle and flow properties (e.g. particle volume fraction, particle and flow Reynolds number, particle-tube radius ratio, inlet conditions) on the interaction between particles and recirculating flow regions such as the corner vortex. Of particular interest is the evolution of particle accumulation or depletion in the vortex, which can be followed by fast imaging methods.