The document describes a procedure to determine the flexural strength or modulus of rupture of concrete through third-point loading tests. Steel molds are used to cast concrete prism specimens of either 100x100x500mm or 150x150x700mm size, depending on the maximum aggregate size. The specimens are loaded in a testing machine with rollers spaced at either 200mm or 133mm until failure. The maximum load at failure is then used to calculate the modulus of rupture according to one of two equations depending on the distance between the line of fracture and the near support.