Oil/water/air data are reported for vertical flow in a 0.026 m i pipe. Nine flow regimes were identified by visual/video and pressure techniques and flow regime maps presented. A relation for determining the transitional boundary between oil and water dominated regimes was presented. Total liquid and individual phasic liquid holdup data in the form of a complex series of curves showing the influence of input liquid flow rates, gas rates and flow pattern were presented. Pure liquid holdup data obeyed existing models for the water system. A new relation was presented for the oil system. Using these models the total liquid holdup against oil/liquid ratio was quantified for annular flow patterns.Pressure loss data are presented as complex curves showing the influence of input fluid rates and flow patterns. Results show that the pressure loss went through a minimum as the gas rate was increased in a similar way to that observed in two-phase flow. A qualitative explanation of the data was presented for annular flow patterns based on the formation and interaction of the various annular/annulus films present.