Experiments were performed in a 50.8 mm diameter horizontal pipe with co-current stratified gas-liquid flow. A single, 6.35 mm diameter, downward oriented discharge was located at 1829 mm from the horizontal pipes inlet. Water and air, operating at a pressure of 312 kPa and adiabatic conditions, were used. The objectives of the study were to investigate gas entrainment in the discharge branch. Qualitative flow visualization of the two-phase entrainment flow structure was conducted, and measurements of the critical liquid height, two-phase mass flow rate, and quality, are provided. The results were compared with available correlations and showed good agreement with selected models.