The study consists in making a discrimination between four fluidized bed reactor models: Davidson and Harrison, Partridge and Rowe, Kunii and Levenspiel, Kato and Wen models. Their predictions are compared with data obtained by carrying out experiments on the catalytic ammoxidation of propylene to acrylonitrile in a 165 mm dia. reactor. These experiments were designed to test the models as selectively as possible. On statistical ground, none of them is acceptable as representing the behaviour of the reactor over the whole range of operating conditions. However, the models of Partridge and Rowe, Kunii and Levenspiel and Kato and Wen lead to rather good predictions on limited ranges of gas flow rate or mass of catalyst. Among them, the bubble assemblage model of Kato and Wen provides the best overall predictions if it is slightly modified by including the wakes of the bubbles with their clouds or by reducing the bubble formation diameter, for instance.