A microspectrofluorometric approach in conjunction with microelectrophoretic injection of glucose-6-P (G6P), was used to study the effect of cultivation in a benzo(a)pyrene (BP)-containing medium on the metabolization of BP, by EL2 ascites cells. The fluorescence increase which follows the microinjection of G6P to single living cells. was studied in EL2 cells grown for 24-hours, 48-hours, 10 days and 57 days in a BP-containing medium, as well as EL2 cells grown for 16 days in presence of BP and placed then for 24 or 48 hours in a BP-free medium. The effects on the induction of Aryl Hydrocarbon Hydroxylase were observed for cells so treated, and it seems that for the latter the requirement of intracellular O2 for the metabolization of BP, has been verified. Furthermore, another important factor has emerged: the intracellular BP concentration. The various spectra are discussed in function of these considerations.