We evaluated, in vitro, the messenger RNA (mRNA) and protein levels of Glut-1 and HKII in MCF-7, a breast adenocarcinoma cell line, and (3)H-FDG uptake, both in untreated conditions and during treatment with either DOX or 5FU for 24 h. Six time points were evaluated: untreated at time 0; treated for 1 h; treated for 24 h; and 1, 2, and 3 d after chemotherapy.