Mucor mycosis is an uncommon saprophytic opportunistic fungus causing localized cutaneous infection associated with high morbidity and, on dissemination, high mortality. We report the case of an immunocompromised patient with an aggressively progressing, painful non-traumatic ulceration, unresponsive to standard treatment. Deep biopsies for haematoxylin and eosin staining and fungal culture revealed the characteristic broad non-septate irregular hyphae of mucor allowing introduction of the appropriate treatment. Infection with mucor mycosis must be considered in today's medical environment as the number of immunocompromised patients increases.