During antifungal screening of some essential oils, Foeniculum vulgare exhibited the strongest activity, completely inhibiting the mycelial growth of the nail-infective fungi, Trichophyton rubrum, T. mentagrophytes and Scytalidium dimidiatum. The essential oil was found to be fungicidal at 0.2, 0.4 and 0.5 µl/ml concentrations. The oil was efficiently active against heavy doses of inoculum at minimum fungicidal concentrations. The fungicidal activity of the oil was found to be thermostable up to 80°C, with no descramble decrease in activity after 48 months of storage. The oil also showed a broad fungitoxic spectrum, inhibiting the mycelial growth of other nail-infective fungi, viz. Aspergillus flavus, A. fumigatus, A. niger, A. ustus, Candida albicans, Epidermophyton floccosum, Microporum audouinii , M. canis, M. gypseum, M. nanum, Rhizopus nigricans, Trichophyton tonsurans and T. violaceum. Moreover, it did not exhibit any adverse effects on mammalian skin and nails up to 5% concentration. As such, the oil has a potential use as an effective herbal chemotherapeutic after undergoing successful clinical trials.