The author has investigated a specific fungiostatic action against Candida albicans Tanimoto by using 109 different species of photosensitizing dyes, classifing them into groups according to their constitutional formulas. Among so many species photosensitizing dye NK 91 which belongs to Styril type showed the strongest fungiostatic action and scareely decreased its effect by adding serum. The results obtained can be summarized as follows: 1) In respect of the types of dyes, Monomethin, Trimethin, Heptamethin, Cyanin and Styril types showed a strong fungiostatic action. 2) In respect of the radical nucleus (of dyes, Benzothiazol. Naphtothiazol and Chinorin nucleus showed a moderate fungiostatic action). 3) In respect of the alkyl radical, high alkyl did not always show the fungiostatic effect. 4) In regard to Halogen and acid radical, eight kinds of iodine radical, one kind of bromine radical, and three kinds of acid radical were efficacious. 5) NK 91 changed remarkably the shape of Candida albicans and moreover in the high concentration, perished utterly Candida albicans. 6) NK 91 inhibited the decline of pH of Sabouraud-glucose medium in which Candida albicans was inoculated. 7) The respiration of Candida albicans was inhibited and its oxygen consumption lowered by NK 91.