Eight non-ionic, cationic, anionic and amphoteric surface-active comps. with perfluorinated alkyl substituents were studied for surface tension and foam-forming ability in aq. solns. The surface tension of the solns. and crit. micelle concn. decreased with increasing the length of the perfluorinated alkyl chain. The compds. with short perfluorinated alkyl chains did not show any foam-forming capacity.