Pressure-drop and phase-distribution data were generated for air-water flows in a horizontal impacting tee junction. All three sides of the junction (37.8-mm i.d.) were oriented horizontally. The data correspond to a junction pressure of 1.5 bar (abs), ambient temperature, inlet flow regimes of wavy, stratified, and annular, and a wide range of mass splits at the junction. Most of the range for the phase-distribution data corresponds to conditions that were untested in previous investigations. In general, it was found that the phases did not distribute themselves evenly between the two outlets unless the mass split is equal. There is a serious lack of data in the literature on the two-phase pressure drop in impacting tee junctions and therefore, the present data add substantially to the existing data. A mechanistic model capable of predicting the phase distribution and pressure drop was developed and shown to be in general good agreement with the present data and others from the literature. (C) 2006 Elsevier Ltd. All rights reserved.