The performance of a journal bearing is studied by using the Reynolds equation. To maintain the normal performance, the lubricant must be supplied from external source in a volume required to flow out at the both sides of the bearing. When the supply rate is reduced, the distribution of the effective oil film is moved to the rotational direction according to the side flow rate. Under this assumption, the bearing characteristics, eccentricity, attitude angle, maximum film pressure and coefficients of friction are calculated and schematized with reference to the Sommerfeld numbers and the lubricant supply rate. Moreover allowing for the variation of viscosity with temperature, an equation is delivered to calculate the oil film temperature. Experimental results, which were obtained with a test bearing of 100 mm in length and 100 mm in diameter, show a good agreement with the calculated values.