Data on the energy losses for particles incident on various target materials are needed in medical applications and other areas. The existing studies on the energy losses of positrons with low energy are very limited. In this paper, the stopping power calculations are presented for positrons in the energy range of 10 eV-10 keV. Target materials considered in this study are water, brain, and lung. Parameterizations of the energy dependencies of the stopping powers of positrons in water and hydrogen up to 100 eV and from 100 eV to 1 keV are obtained. Also, the maximum stopping powers versus the atomic numbers of various elements in water, brain, and lung are examined. The results are compared with other studies. © 2012 The Physical Society of the Republic of China.