An experimental study of the droplet size and velocity distributions in gas-liquid annular upflow is reported for a 50.8 mm i.d. vertical tube. Included are the effects of liquid viscosity and the radial variation of drop size and velocity. Additional measurements of the centerline gas velocity are used to estimate the gas-droplet slip ratio. The drop size distributions exhibit a bimodal nature, discounting the use of previously suggested functions for their description. Mean drop sizes are observed to increase with liquid flow rate and viscosity. On average, droplets at the tube centerline are observed to travel at 80% of the local gas velocity.