A study was made of the film characteristics and the local heat transfer coefficients for the downward flow of steam condensing in a vertical tube. The mass velocity of the steam was such that the flow occurred in the annular-mist regime. The interfacial wave velocities, frequencies, and amplitudes were experimentally determined using needle contact probes. From these data on wave characteristics a statistical wave form was obtained. The liquid mass flow occurring in identifiable waves was determined from a numerical integration over the disturbance layer (i.e., that portion of the liquid layer in which waves are present) and compared to the liquid mass flow given by an energy balance and an entrainment correlation. The results indicated a heavy concentration of liquid particle entrainment in the neighborhood of the film. In addition, the axial profiles of the local heat fluxes and local heat transfer coefficients across the film were obtained. The film Nusselt number at the location of the probes based on an operationally defined mean film thickness was found to correlate with the product of the dynamic quality and the ratio of liquid to gas densities. / Master of Science