This report describes the development and intended use of the computational phantoms of the Reference Male and Reference Female. In its 2007 Recommendations, ICRP adopted these computational phantoms for forthcoming updates of organ dose coefficients for both internal and external radiation sources (ICRP, 2007). The phantoms are based on medical image data of real people, yet are consistent with the data given in Publication 89 (ICRP, 2002) on the reference anatomical and physiological parameters for both male and female subjects. The reference phantoms are constructed after modifying the voxel models (Golem and Laura) of two individuals whose body height and mass resembled the reference data. The organ masses of both models were adjusted to the ICRP data on the adult Reference Male and Reference Female, without compromising their anatomic realism. This report describes the methods used for this process and the characteristics of the resulting computational phantoms.