Modelling of transport phenomena in the jetting region of fluidized beds requires the specification of several hydrodynamic parameters, one of which is the divergent angle of the jets. A series of experiments was conducted to measure this angle for a vertical jet of gas as it enters a fluidized bed, by the use of X-ray imaging techniques. In all the tests the material surrounding the jet was maintained in a fluidized state by a separate gas flow. Results were obtained for a number of different particulate materials fluidized at ambient conditions, and at high temperature and high pressure. Variations were also made to the orifice gas velocity and the orifice size. Generally the jet angle is shown to decrease with increasing operating pressure, to increase with increasing bed temperature, and to decrease with increasing orifice gas velocity. The dependence of orifice size on the jet angle was somewhat ambiguous, although larger orifice sizes resulted in significantly larger jet angles in some cases.