Commercial antifungal drugs possess important side effect; being toxicity the main limitation of such compounds. We report here a study of acute toxicity of four well-known commercial antifungal drugs; two of them used in human medicine (griseofulvine and miconazole) and the other two used against phytopatogens fungi (carbendazin and benomil). Toxic effects of these compounds were evaluated using an acute toxicity test on fish of the specie Poecilia reticulata.