Water Velocities inside a 150mm Krebs™ DF6 classifying hydrocyclone have been measured using an Aeroprobe™. Although the Aeroprobe disturbs the flow, the axial and tangential velocity measurements are qualitatively sensible and the integral wall pressure obtained from the measured tangential velocity profile is close to the measured wall pressure at the same elevation, which suggests that the measured tangential velocities are still reasonably accurate. The time averaged velocities from Large Eddy Simulations of the same cyclone geometry in Fluent™ are within 15% of the measured velocities.