This paper investigates the cure kinetics for the ultraviolet (UV) cationic polymerization for both a cycloaliphatic and diglycidyl ether of bisphenol-A (DGEBA) epoxy system, using the photoinitiator triarylsulfonium hexafluoroantimonate salt, Using an autocatalytic kinetic cure model, the reaction rate values for both cycloaliphatic and DGEBA epoxy systems were determined for different photoinitiator amount (wt %) added, and at different UV exposure temperatures. The value for the cycloaliphatic epoxy increased significantly with addition of the sulfonium salt, reaching a limiting maximum after 2%. The value for the DGEBA epoxy system also increased, to a limiting maximum after 3%. Addition of the sulfonium salt significantly lowered the activation energy for the cycloaliphatic epoxy at all levels of addition, with the reduction proportional to the amount of salt added. In contrast, the sulfonium salt did not have a major effect on the DEGBA until the addition of at least 3% of the salt.