Multiphase oil/water/gas flow regime transition studies are carried out in a 10-cm I.D., 18-m long Plexiglas pipe at inclinations of ±2° at system pressures up to 0.79 MPa. The results are compared to those of other researchers, and the effects of pressure, inclination and liquid viscosity are shown. The water cut of the liquid has some effects on the transitions from stratified to slug flow. Increasing the water cut results in the transition occurring at higher liquid velocity at the same gas velocity. Water cut has little effect on the slug/annular transition for the low viscosity oil used. The system pressure has a small effect on the transition from stratified to slug and slug to annular. For the transition from stratified to slug, increasing the system pressure, requires higher liquid velocity. The transition from slug to annular occurs at lower liquid velocity with increasing system pressures. The inclination of the pipe has an effect on the transition from slug to annular flow. Increasing the inclination causes the transition to occur at lower gas velocity at the same liquid velocity.