Imaging time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to study the localization of heterocyclic amines in MCF-7 line of human breast cancer cells. The detection sensitivities of amodel rodentmutagen, 2-amino-l-methyl-6phenylimidazo[4,5-b]pyridine (PhIP), were determined. Following an established criteria for the determination of status of freeze-fracture cells, the distribution of PhIP in the MCF-7 cells was reported. (C) 2004 Published by Elsevier B.V.