A relatively large number of animal models of candidosis exist in which the efficacy of antifungal substances can be evaluated. These include models of candidosis of the skin, gastrointestinal tract, genital system, and internal organs in a variety of animal species. The efficacy of ketoconazole administered orally and topically was evaluated; when given orally in relatively low doses, ketoconazole was found to be efficacious in all of the experimental models used. Scanning and transmission electron micrographs of infected tissue demonstrated the rapidity with which Candida albicans was eradicated from the host after administration of ketoconazole.