ASTM F903, the standard method for measuring the resistance of protective clothing materials to penetration by liquid chemicals, was first introduced in 1987. Since this time, extensive experience has been gained with its use and the application of penetration resistance data. The method involves placing a material in a test cell which allows one-sided contact of the specimen with a liquid chemical. In its newest revision, the length of exposure and pressure applied behind the chemical may be chosen by the laboratory and can impact test results. Penetration is detected visually but may be enhanced by a number of techniques. Interpreting penetration results requires an understanding of ways different material specimens may fail. Test specimens other than flat materials may be accommodated within the test cell using special gaskets or sealing methods. Penetration resistance data is not widely used by the chemical protective clothing industry. Most clothing manufacturers choose to report permeation resistance data for their products. However, the choice of permeation versus penetration testing is dependent on the type of protection desired and the relative hazards of the environment. Penetration testing offers a viable means of demonstrating protective clothing material barrier performance against liquids and as such is suited as the appropriate chemical resistance test for liquid splash-protective clothing.