The exact pathogenesis of chromoblastomycosis is unknown. Direct percutaneous inoculation, inhalation, and hematogenous dissemination have been implicated. We report a case of chromoblastomycosis that followed a well-defined episode of penetrating trauma. The causative organism, Fonsecaea pedrosi, was cultured from the patient's lesion and from the tree branch responsible for the trauma. This "natural" experiment supports the contention that one cause of chromoblastomycosis is traumatic cutaneous implantation of the fungus.