The effects of both Salmonella typhimurium infection and 5 mM ofloxacin treatment on 2 mM glutamine and 5 mM glucose metabolism in the enterocyte-like Caco-2/TC-7 cell line were studied. These cells utilized glutamine (212.07 ± 16.75 [mean ± standard deviation] nmol per h per 10⁶ viable cells) and, to a lesser extent, glucose (139.63 ± 11.52 nmol per h per 10⁶ viable cells). Metabolism of these substrates in Caco-2/TC-7 cells resembled that in rat, pig, or human enterocytes. Infection by S. typhimurium C53-enhanced glucose and glutamine substrate utilization by 32 and 22%, respectively and enhanced glucose and glutamine substrate oxidation by eight- and twofold, respectively. These increases in glucose and glutamine metabolism (especially glucose metabolism) were due in part to the metabolism of intracellular bacteria and/or to the activation of cellular metabolism. Substrate metabolism (especially glucose metabolism) in C53-infected cells was partially reduced by treatment with ofloxacin. It was concluded that cellular fuel metabolism is stimulated at the earliest stage of infection (3 to 4 h) and that treatment with 5 mM ofloxacin does not completely restore substrate metabolism to the levels observed in uninfected cells, possibly because this treatment does not eradicate intracellular S. typhimurium completely.