Topsin M is a common systemic fungicide used as protective/curative substance for alimentary and medicinal plants. That is why it is relevant to evaluate the influence of Topsin M upon the anatomical features of Mentha longifolia, a volatile oil producing medicinal plant and parental species for the hybrid Mentha×piperita. We analysed the anatomical features using cross section through vegetative organs (stems and leaves) belonging to treated and untreated plants. The structure of epidermis in the leaves of Mentha longifolia L. (Huds.) was studied by scanning electron microscopy (SEM).We noticed more quantitative changes than qualitative changes under antifungal Topsin M treatment.