For a vertical plunging liquid jet system using various liquids, the effects of the operating conditions including the nozzle length-to-diameter ratio on the gas entrainment rate Q, were evaluated experimentally. The differences in Q, were related to the changes in the jet shape before plunging and the velocity of the plunging liquid jet at the point where the gas sheath breaks up. Empirical relationships were also presented to predict the maximum depth Z of bubbles entrained by the diffusing jet. The changes of Z were further discussed in terms of the downward liquid velocity distribution in the submerged two-phase region, which depends mainly on the size of entrained bubbles.On a evalue de faqon experimentale pour un systkme a jet liquide plongeant utilisant des liquides varies, les effets des conditions d'opkration, notamment le rapport entre la longueur et le diamktre de l'orifice sur la vitesse d'entraineinent du gaz Q,. Les differences dans Q, ont Ct6 relikes aux changements dans la forme du jet avant l'immersion et B la vitesse du jet liquide plongeant au point ou I'enveloppe du gaz se brise. On a Cgalement present& des relations empiriques pour prCdire la profondeur maximum Z des bulles entrainees par le jet diffusant. Les changements dans Z ont ensuite CtC examines par rapport a la distribution de la vitesse liquide descendante dans la region biphasique immergee, qui depend principalement de la taille des bulles entrainkes.