Utility of the hot-film anemometry technique in describing the internal flow structure of a horizontal slug flow-pattern is discussed within the scope of intermittent nature of slug flow, It is shown that a single probe can be used for identifying the gas and liquid phases and for differentiating the large elongated bubble group from the small bubbles present in the liquid slug. Analyzing the nature of voltage signals, a signal processing scheme is developed for measurements of time-averaged void fractions of small and large bubbles as well as for the measurements of local mean axial velocity and turbulent intensity in the liquid phase. Some results of local measurements of time-averaged void fractions of small and large bubble groups, axial mean velocity and turbulent intensity are presented at relatively low and high gas and liquid flows for a horizontal slug flow-pattern in a 50.3 mm i.d. pipe.