The paper describes an interferometric method of determining the shape and thickness of the clastohydrodynamic oil film formed between a rotating ball loaded against a diamond, sapphire, or glass plate, and a rotating roller loaded against a glass plate. The film shape for both point and line contact is found to depend critically on speed and load. It is found that considerable departure from the static Hertzian shape occurs at quite low speeds. The line contact results show the extent of the end closure and its dependence on the blend radius of the roller.Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Minneapolis, Minnesota, October 18–20, 1966.