An international interlaboratory comparison for numerical calculations  of head phantom SAR involving three mobile phones with computer-aided  design-based models has been conducted in order to evaluate the  repeatability of such calculations and for providing input in the  development of standardized procedures. SAR in the SAM head phantom was calculated by ten  laboratories in a blind study manner. The agreement in the  results ranged from good to  poor and supports the opinion that standardized procedures for numerical  calculations of SAR can be developed. Most likely a significant reason for  the observed deviations is simplifications made to the models,  which implies that device modeling specifications are of utmost  importance in standards.