Cutaneous protothecosis sometimes poses diagnostic and therapeutic problems. Isolation of the causative organism may not be successful and spores may be mistaken for other skin diseases unless the characteristic sporangia are detected in tissue sections. Because there are few cases, the optimal therapy is still being debated. On Liebs crystal violet staining we found charateristic purplish dots in Prototheca spores; these correspond to the amyloplasts or dense bodies found under electron microscopy. The isolated organisms were inhibited in vitro by itraconazole, amphotericin B, ketoconazole, and amorolfine and we were able to successfully treat two patients with itraconazole.