Detailed hydodynamic measurements have been obtained for fully cylindrical spout-fluid beds of 1.3 mm; 1.8 mm and 2.5 mm glass beads in a fully cylindrical column of diameter 152 mm using three different types of optical fibre probes. The reallocation of up to 43% of the air to auxiliary air introduced through the conical base caused some decrease in spout voidages, but remarkably little change in spout diameter compared with spouted beds where there was no auxiliary air addition. Auxiliary air led also to same decrease in particle velocities in the spout and to a modest decrease in the net solids circulation rate.