Mature S. cerevisiae and C. glabrata biofilms have similar sensitivity to antifungal drugs. Antifungal drug activity against 48-hour biofilms was visualized by confocal laser scanning microscopy. GFP-tagged S. cerevisiae was stained with propidium iodide (PI, 1 μM) to mark living (green) and dead (red) cells. C. glabrata was stained with Syto9 (3 μM) and PI (1 μM) to mark living (green) and dead (red/yellow) cells. Biofilm cells were treated for 24 hours with the indicated antifungal agents. VOR: voriconazole (10 μg/ml for S. cerevisiae and 50 μg/ml for C. glabrata), 5FC: flucytosine (80 μg/ml), CAS: caspofungin (10 μg/ml for S. cerevisiae and 5 μg/ml for C. glabrata), and AmB: amphotericin B (10 μg/ml for S. cerevisiae and 20 μg/ml for C. glabrata).