Investigations into the flow pattern and the void fraction for countercurrent air-water flow in vertical tubes of diameter D = 40 and 80 mm were reported. The flow maps were presented and showed slug flow regime occupied larger portion on them. The void fraction was measured by the quick-closing valve technique, in bubbly and slug flow regime. The void fraction data available in the literatures as well as present work for counter- current flow in vertical tubes were correlated in terms of dimensionless groups. The experimental results of the present work were also compared with the drift flux model.