The aim of the present work is to provide unsteady experimental data about the flow in a one-stage axial compressor. Some particular flow features are described and discussed. The operating conditions considered here concern an off-design point that is close to the compressor rotating stall limit. Measurements were performed with a three-dimensional laser Doppler velocimeter. Twenty-eight axial sections were surveyed from the rotor inlet to the stator outlet. In each section, velocity and velocity fluctuation measurements concerned more than 250 points. Thus, more than 8000 locations of measurement were investigated in the rotating and in the fixed parts of the stage. The main flow patterns associated with the rotor unsteadiness are described through a few pictures of the measured velocity components and of the Reynolds-stress distributions. Obviously, the most outstanding flow phenomena occur in the upper part of the rotor channels and take place along the stator blades suction side. In the moving row, secondary complex flow structures are highlighted, and the structure of the separated flow along the stator blade is analyzed. NomenclatureC x = axial blade chord at midspan (e b , e g , e y ) = unity vectors of the color frame of reference f −1 RTR = rotor blade passing period H = channel height h = height k = phase of a collected samplė m = mass-flow rate R tip = radius at rotor-blade tip U = peripheral velocity of the rotor blades, = · R tip V = absolute velocity V = absolute velocity vector in the cylindrical compressor frame V color = velocity vector in the color frame of reference W = relative velocity W = relative velocity vector in the cylindrical compressor frame (x, R, θ) = cylindrical system of coordinates (x is the engine axis) θ RTR = azimuthal coordinate in the cylindrical relative frame of the rotor λ = color wavelength τ xx = component of the Reynolds tensor in the axial direction τ xθ = component of the Reynolds tensor in the x, θ direction τ θθ = component of the Reynolds tensor in the tangential direction Subscripts b = relative to the blue (λ = 488 nm) color g = relative to the green (λ = 514 nm) color RTR = relative to the rotor STR = relative to the stator y = relative to the yellow-green (λ = 532 nm) color = rotor angular velocity Superscripts -= steady mean value ∼ = phase-averaged value = turbulent fluctuation