In this chapter, the authors attempt to illustrate the utilisation of supercritical carbon dioxide (scCO2) as a suitable alternative to conventional organic solvents in numerous different synthetic polymerisation processes by giving an overview of recent literature in this area. There are a host of opportunities in polymer science as a result of the unique characteristics associated with scCO2. The use of this solvent leads to the generation of polymeric products possessing well-defined structures (particles with well-defined morphologies) and properties. The literature has shown the versatility of scCO2, with its successful implementation in a variety of different polymerisation processes including step-growth polymerisation, chain-growth homogeneous polymerisation, precipitation polymerisation, dispersion polymerisation, suspension polymerisation and emulsion polymerisation. It is a particularly attractive medium for precipitation and dispersion polymerisations due to the insolubility of numerous high molecular weight polymers in scCO2. It has been shown that scCO2 is ideal for conducting heterogeneous controlled living radical polymerisation (CLRP) since the monomer, control reagents and initiator are completely soluble in scCO2 but the resultant polymer is not and precipitates out. This results in the polymer only being able to continue to grow in the particle phase, leading to a living polymer having a microstructure that is controlled and well-defined.