Epidemiological studies investigating whether mobile phone use is related to cancer risk have been conducted in many countries. The purpose of the work reported here was to introduce the dose metric in the exposure assessment, taking into account the spatial distribution of exposure. Distributions of specific absorption rate (SAR) inside 275 cases of brain tumors (participants in the Japanese epidemiological study) were estimated. Phones had been classified into four categories based on SAR distributions and technical specifications. Results were found to be highly dependent on phone categories. Contralateral tumors were generally categorized as non-exposed tumors (max SAR <2.5% of max SAR in the brain) and, for any phone category, the maximum SAR in 75% of the ipsilateral tumors was less than 15% of the maximum SAR in the brain. Three new exposure indices combining the duration and strength of exposure were created to be used in the Japanese epidemiological study on mobile phone use and the risk of gliomas and meningiomas.