Perfluorocarbon (PFC) nanodroplets formed from PEG-b-poly(fluoroheptyl aspartate) were developed for a cancer-targeted ultrasound (US) contrast agent. 10% esterifed fluoroalkyl polymer (F10) was the optimal composition for PFC solubilization in aqueous solution. PFC/F10 nanodroplets showed echogenicity with US irradiation, and long-term stability of PFC nanodroplets at 4 degrees C was confirmed.