Various boundary conditions of fluid lubrication theories have been presented for the trailing edge of the lubricant film of a journal bearing, but they do not seem to be clearly investigated physically in connection with the lubricant film rupture. The reverse flow and, hence, the separation of fluid are observed experimentally to cause the film rupture. This condition is brought to be the boundary condition of the bearing film rupture in this paper. By using this condition, the bearing characteristics, such as eccentricity, load capacity, and attitude angle, are investigated theoretically. The experimental results, obtained by using the transparent bearing for the direct observation of the bearing film behavior, agree well with the theoretical ones.Presented at the 23rd ASLE Annual Meeting in Cleveland, May 6–9, 1968.