The interaction between a single jet and a bed of fluidized solids was investigated with the aim of evaluating a characteristic height of the jetting region corresponding to the distance from the nozzle at which the dispersion of jet momentum is practically complete. A new experimental technique, based on simultaneous measurements of the static pressure at the bed side wall and on the jet axis and on their elaboration, was used. Various experimental configurations, based on the combination of two fluidization columns (0.35 and 0.20 m, i.d.) and four jet nozzles (6, 10, 19 and 25 mm, i.d.), were employed. Glass ballotini of 800-1200 mu m were used as bed material. The influence of the nozzle gas velocity, of the fluidization velocity, and of the nozzle and the column sizes on the characteristic height of the jet was investigated. This height increases as nozzle gas velocity and nozzle size increase. In contrast, the influence of the fluidization velocity appears more complex and, in particular, cannot be separated from that of the nozzle diameter. The effect of the column diameter was negligible. Experimental results were compared with predictions of jet penetration length from literature correlations since the characteristic height shows up evident similarities with the jet penetration length based on momentum dissipation.