This paper discusses a new downhole logging instrument that measures three-phase flow in horizontal and highly deviated wells. The focus is on the instrument design features, and the measurement techniques that produce the three-phase holdup and velocity measurements. Signals from a two dimensional array of capacitive sensors ave measured, and subsequent processing determines the volume fraction and velocity of each component of the borehole flow. The design incorporates an army of capacitive sensors that span the wellbore. Since two orthogonal electrical signals are used to excite local fluid elements, it is possible to determine the fluid capacitance or the volume fraction of conductive fluid in. the vicinity of each sensor. Holdups are calculated from these sensor outputs. Velocities are calculated by correlating outputs from adjacent sensors. Measurements concepts and instrument characterization are demonstrated with flow loop data. [S0195-0738(00)00802-5].