This chapter describes polymer flooding applications as a mobility control and profile modification process to enhance oil recovery from mature fields. Successful experience from the Daqing Oilfield, the largest oil field application of polymer flooding, is summarized. The experience will be of considerable value to future polymer flood applications elsewhere in oil fields with appropriate reservoir conditions. Based on laboratory research and field applications at Daqing, technologies were developed that expand conventional ideas concerning favorable conditions for mobility improvement by polymer flooding. These include: 1. The oil strata and well pattern design should be optimized and integrated considering interwell connectivity and permeability differential among the oil zones. 2. The injection procedures and formulation are the key points when designing a polymer project—such as profile modification before polymer injection and zone isolation during polymer injection, higher molecular weight (MW) of the polymer used in the injected slugs, large polymer bank size, higher polymer concentrations and injection rate based on the well spacing, and injection pressure. 3. Surface mixing, injection facilities, oil production, and produced water treatment are important to reservoir engineering aspects of polymer flooding.