The aim was the investigation of fungal colonization and morphological alterations under the influence of voriconazole in an in vitro system. Voriconazole stopped growth and colonization of Candida albicans (wild type SC5314) on cover slips in microtiter plates dependent on drug concentration, the time of Candida growth before the input of voriconazole and oxygen concentration. The direct microscopy by fluorescence staining with the optical brightener Blancophor showed short bizarrely deformed mycelia looking swollen. The colonization on cover glass was diminished. Microcolonies or starting of biofilm formation as in the control was not observed. The metabolic activity was demonstrated by vital staining with FUN 1 resulting in red fluorescent structures in the yeast forms and mycelia in the controls. Under voriconazole influence the remaining cells only showed a green or pale yellow fluorescence. Most of the cells lost their metabolic activity.