Abstract: A process is described for infusing an additive into a polymer using a compressed fluid that is normally a gas at room temperature and pressure. The additive must have some degree of solubility in the compressed fluid and the solution of compressed fluid and additive must have some degree of solubility in the polymer. In accordance with the process, the solution of the normally gaseous fluid and additive and the polymer are brought into contact under pressure until a desired quantity of the solution is absorbed into the polymer. The compressed fluid then is diffused from the polymer leaving additive infused within the polymer. The process can be used, for example, to add a colorant to a polymer or to add a biocide, insect repellant, medication or other additives to a polymer for subsequent sustained release, or to introduce monomer and a polymerization initiator into a polymer for subsequent polymerization.