Past studies have shown that liquid jet breakup behavior can be classified into five regimes: Rayleigh, first wind, sinuous, second wind, and atomization. By experimentally examining the breakup of superfluid and normal liquid 4 He in an atmosphere of its own vapor, we investigate the evolution of the jet behavior over a large range of the traditional three-dimensional parameter space of the Ohnesorge number [Oh l∼O ( 10−5–10−2)], Reynolds number [Rel ∼O(102–106)], and gas-liquid density ratio [ρg/ρl∼O(10−4–1)]. Using dimensional analysis we find that the transition from Rayleigh to first-wind breakup occurs at a constant liquid Weber number, and that the transitions from first wind to sinuous, and sinuous to second wind occur at constant gas Weber numbers. The proposed transitions, which differ from some previous studies, are well supported by our new experimental data that extend over all three dimensions of the parameter space. We do not observe any obvious effects of superfluidity on the breakup behavior. In addition, we examine the breakup length and comment on the transition of a liquid jet to a gaseous jet as the temperature passes through the critical point.