The surfactant properties of amphiphilic hyperbranched polyglycerols (HPGs) were investigated. The HPGs were prepared by ring-opening multibranching polymerization of glycidol using hydrophobic initiators of varying size and structure. The cloud points for all HPG surfactants were found to be >80 degrees C in deionized water with >1 wt % NaCl. The HPG surfactants with hydrophilic-lipophilic balance values between 16 and 18 were found to form stable octanol/water (o/w) emulsions within a 24 h period. Several surface properties, including critical micelle concentration (CMC), efficiency of surface tension reduction (pC(20)), effectiveness of surface tension reduction (gamma(cmc)), surface excess concentration at the CMC (Gamma(max)) minimum area/molecule at the interface (A(min)), and the CMC/C-20 ratio of the HPG surfactants were measured in deionized water at 22.6 degrees C. In general, increasing HPG size was marked by an increase in minimum surface area per molecule (A(min)) at the aqueous liquid/air interface. This increase in size also led to lower CMC and greater pC(20) values of HPG surfactants prepared with Tergitol 15-5-7 initiator (HPG 5a-5d), a commercially available ethylene glycol oligomer with a branched hydrophobic tail.