A unified approach for predicting the transition to dispersed flow patterns in gas-liquid and liquid-liquid systems is suggested. It is based on the revised models for predicting the maximal drop size in a turbulent field which account for the holdup of the dispersed phase. Examining the range of applicability of the various models for transition to dispersed flow indicates that it is determined by the Eötvös number, EoD=ΔρgD2/8σ. Comparisons with available experimental data for gas-liquid and oil-water systems show that these models are capable of predicting the effects of fluids' physical properties, tube diameter and inclination. The models suggest a non-monotomic effect of the tube diameter on the critical fluids' flow rates, which implies that the up-scaling of data should be approached with care.