Two cases of infection caused by Prototheca, belonging to the colourless algae, are discussed. In one of the patients colpitis, in the other one disease of the cubital bursa developed due to Prototheca. In the first case recovery was attained with tetracyclin, in the second case with surgical treatment. Microbiology, epidemiology, pathology and clinical aspects of the insufficiently known in Hungary protothecosis are outlined.