The goal of this study is to develop new indices, which effectively evaluate dose homogeneity of intensitymodulated radiotherapy (IMRT) treatment plans with dose– volume histogram (DVH). The newly defined homogeneity indices for assessing dose homogeneity in a target volume, named s-index and n-index, were developed using a normalized differential-DVH (dDVH) and functional approximation of DVH, respectively. Although both indices have been demonstrated to be more accurate than the conventional methods in evaluating the dose homogeneity, the results showed the sindex is more consistent method for quantifying the degree of homogeneity. The s-index, determined as the standard deviation of the normalized dDVH, was found to vary from 0.80 to 3.15 for 16 brain tumor patients at out institution. A guideline of the treatment plan based on s-index for dose homogeneity is discussed with relation to equivalent uniform dose (EUD).