Abstract: This paper describes some experimental studies about the influences of grooved surface on the film thickness of hydrodynamic lubrication by a custom-made test apparatus. In the experiments, the lubricated parallel contact consisted of a micro-slider plane and a transparent glass disc. Under a fixed load (speed), the film thickness at different entrainment speeds (load) was measured. The results show that the width, depth, orientation and position of the groove were the key factors to affect the film thickness. Furthermore, the classical Reynolds equation was used to calculate the film thickness. Comparisons between theoretical analysis and experiments show that the classic Reynolds equation cannot always be used to predict the surface texture effect. Keywords: conformal contacts, grooved surface, hydrodynamic lubrication, film thickness