An optical fiber probe has been used to study the effect of operating conditions (base angle, gas inlet diameter, stagnant bed height, particle diameter and gas velocity) on particle velocity in the three zones of spouted beds: spout, annulus and fountain. The experimental results prove the validity of the equation of Epstein and Grace (1984) for prediction of the vertical component of particle velocity in the spout by establishing the relationship of the parameter of this equation with operating conditions. It also been proven that the equation of Mathur and Epstein (1974) is valid for predicting particle velocity in the fountain core. From the values of vertical components (experimental) and horizontal components (calculated) of particle velocity, maps of velocity vector throughout the bed have been drawn and zones of preferential solid cross-flow into the spout have been determined.