Abstract： Objective To determine the in vitro antifungal effects of closantel against Candida albicans.Methods A microdilution method was used to determine the minimum inhibitory concentration (MIC)of fluconazole alone and in combination with closantel against Candida albicans standard strain CAF-2.Ten strains of Candida albicans were cultured in RPMI-1640 liquid culture containing 10％ calf serum with or without the presence of closantel at 16 mg/L,followed by the observation of hypha formation.Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were performed to observe the ultrastructure of Candida albicans CAF-2 strain after exposure to closantel at 16 mg/L for 24 hours.Results Closantel could inhibit the growth of Candida albicans,and enhance the antifungal effect of fluconazole against Candida albicans in vitro.The percentage of Candida albicans forming hypha was 91.2％ ± 3.9％ in untreated Candida albicans,significantly higher than that in closantel-treated Candida albicans (29.8％ ± 5.1％,t =30.24,P ＜ 0.05).As TEM showed,closantel-treated Candida albicans gave a round,oval or pleomorphic appearance,with an irregular budding from the cell surface.Further more,the electron dense layer in the outer layer of cell wall was absent or unevenly distributed,the transparent layer was irregularly thickened,some cell membrane was locally disrupted or collapsed,and intracellular vacuoles increased after closantel treatment.Scanning microscopy revealed a rough surface,sparse and irregular budding of Candida albicans after treatment with closantel.Conclusion Closantel exhibits a promising anti-Candida albicans property in vitro.