Gel formation theory is discussed in the case of chemically amplified resists (CARs) and a specific epoxy-based resist is used in order to model the results. It is found that existing gel formation models may be classified in four classes and there are two important parameters (inhibitor activity and maximum number of available crosslinkable sites) which must be specially interpreted in order to account for chemical amplification and diffusion mechanisms in CARs. It is also proved that a Charlesby–Pinner representation of the gel-dose relationship reveals qualitative characteristics of the process and composition changes.