A variety of polymers are used in modern surgical repair. They may be degradable or non-degradable. The most important non-degradable polymer is polyethylene, which in its ultrahigh molar mass (molecular weight) form is widely used in orthopaedic surgery. Another important material in orthopaedics is so-called bone cement, a self-curing poly(methyl methacrylate) system. In addition, there are various degradable polymers, with uses as temporary fixation devices, as drug delivery devices and also as scaffolds in tissue engineering. Hydrogels are considered in their various applications, with their main use in ophthalmology being covered in detail. Lastly, there are silicones, which find application in devices that have a cosmetic component to their use. This chapter covers all of these materials and gives a brief account of their clinical uses. Their biocompatibility in the particular surgical use is also considered in each case.