Counter-current flow limitation (CCFL), the void fraction α, the wall friction factor fw, and the interfacial friction factor fi depend on the shapes of the top and bottom ends of vertical pipes, i.e., the sharp top end and round bottom end (SR), round top end and sharp bottom end (RS), and round top and bottom ends (RR). We observed flow structures with a high-speed video camera and measured CCFL (the relationship between superficial velocities of up-flow gas and down-flow liquid), pressure gradient dP/dz, and α in a RR vertical pipe with the diameter of 20 mm, and working fluids of air and water under flooding conditions, and we obtained fw and fi by using the annular flow model. The feature of flow structures in RR was occurrence of disturbance waves inside the vertical pipe, while they mainly appear at the bottom end in SR and RS. The liquid volume fraction (1−α), dimensionless pressure gradient −(dP/dz) * , and fi in RR for rough film were the same as those for rough film in SR and RS. (1−α), −(dP/dz) * , fw, and fi in RR for smooth film were close to those in SR for smooth film but they were larger than those in SR due to larger falling liquid volume fraction. The upward velocity of disturbance waves was also discussed.