The pulp and paper industry traditionally measures a property called ISO-brightness based on a filter function with an effective wavelength of 457 nm, but this is not a satisfactory measure of the appearance of the material. Currently there is a growing interest in determining a whiteness value based on the CIE-whiteness equation with respect both to an indoor illumination and to the standardized D65 illuminant. This is not, however, merely a question of using the relevant mathematical functions. Many papers contain fluorescent whitening agents and this means that reproducible values can be obtained only if the instruments used are adjusted so that the relative UV-content in the illumination falling on the sample is controlled to correspond to the chosen illuminant. The paper industry employs instruments with a well-defined d/O degrees geometry and the relevant ISO-Standards also define a hierarchical calibration system, which enables all instruments to be calibrated with traceability to the perfect reflecting diffuser through a reference instrument. This calibration service has now been extended to include fluorescent standards assigned whiteness (D65/10 degrees) values. This article describes the development of this calibration routine based on the absolute two-monochromator instrument at BAM, Berlin.