An epoxy resin based on bisphenol-A-diglycidylether (DGEBA) was cured with dicyandiamide (DDA) and different substituted ureas (Urones) as accelerators. Differential scanning calorimetry, size exclusion chromatography, and Fourier transform infrared (IR) analysis indicated complex reaction mechanisms. The DDA granulometry seemed not to be a predominant parameter, but its content clearly influences T-g of the network. The maximum T-g value was found for an amine-to-epoxy molar ratio of 0.6. IR spectra revealed the appearance of oxazolidone rings, which are the first product of epoxy reactions. Urone accelerators also acted as homopolymerization initiators; they modified the epoxy conversion at gelation and changed of the structure of the obtained network. Influence of uron nature and content on reaction rates were also studied.