AbstractA line‐scan echo planar spectroscopic imaging (LSEPSI) sequence was used to serially acquire spectra from 4096 voxels every 6.4 s throughout the breasts of nine female subjects in vivo. Data from the serial acquisitions were analyzed to determine the potential of the technique to characterize temperature changes using either the water frequency alone or the water‐methylene frequency difference. Fluctuations of the apparent temperature change under these conditions of no heating were smallest using the water‐methylene frequency difference, most probably due to a substantial reduction of motion effects both within and without the imaged plane. The approach offers considerable advantages over other methods for temperature change monitoring in the breast with magnetic resonance but suffers from some limitations, including the unavailability of lipid and water resonances in some voxels as well as a surprisingly large distribution of water‐methylene frequency differences, which may preclude absolute temperature measurement. Magn Reson Med 58:1117–1123, 2007. © 2007 Wiley‐Liss, Inc.