During its 13 th meeting in 1994 the Consultative Committee for Photometry and Radiometry (CCPR) decided to carry out a comparison of luminous responsivity to be organized by the BIPM. This comparison was classified as a key comparison by the 14 th CCPR in 1997 and subsequently named CCPR-K3.b. Fifteen laboratories took part in this comparison by sending calibrated photometers to the BIPM. The photometers were compared with a common set of reference photometers to deduce the relative differences between the calibrations made in the participating laboratories. In this report the details of the procedure and the results are presented.