Local velocity measurements (mean and fluctuational) behind pipe axisymmetric sudden expansion have been obtained with laser-Doppler anemometer techniques. Flows with Reynolds numbers (Re-d) from 1000 to 100 000, for two different values of diameter ratio d/D = (0,53; 0,82) were investigated. Mean velocity distribution, jet boundary, recirculation zones and relative velocity fluctuations behind pipe sudden expansion are presented for various Reynolds numbers.