BACKGROUND Enzymes involved in trehalose metabolism have been proposed as potential targets for new antifungals. To analyse this proposal, the susceptibility to Amphotericin B (AmB) of the C. albicans trehalose-deficient mutant tps1Δ/tps1Δ, was examined. METHODS Determination of endogenous trehalose and antioxidant enzymatic activities as well as RT-PCR analysis in cells subjected to AmB treatments was performed. RESULTS Exponential tps1Δ null cultures showed high degree of cell killing upon exposure to increasing AmB doses respect to CAI.4 parental strain. Reintroduction of the TPS1 gene restored the percentage of cell viability. AmB induced significant synthesis of endogenous trehalose in parental cells, due to the transitory accumulation of TPS1 mRNA or to the moderate activation of trehalose synthase (Tps1p) with the simultaneous deactivation of neutral trehalase (Ntc1p). Since tps1Δ/tps1Δ mutant cells are highly susceptible to acute oxidative stress, the putative antioxidant response to AmB was also measured. A conspicuous activation of catalase and glutathione reductase (GR), but not of superoxide dismutase (SOD), was observed when the two cell types were exposed to high concentrations of AmB (5μg/ml). However, no significant differences were detected between parental and tps1Δ null strains as regards the level of activities. CONCLUSIONS The protective intracellular accumulation of trehalose together with the induction of antioxidant enzymatic defences are worthy mechanisms involved in the resistance of C. albicans to the fungicidal action of AmB. GENERAL SIGNIFICANCE The potential usefulness of trehalose synthesis proteins as an interesting antifungal target is reinforced. More importantly, AmB elicits a complex defensive response in C. albicans.