The curing of a fiberglass epoxy composite based on diglycidyl. ether of bisphenol A (DGEBA) with dicyanodiamide (DDA) as the hardener and imidazole as the catalyst agent was analyzed using microdielectrometry, The curing behavior of thick epoxy composite parts was examined in a production environment for compression molding process; The particular focus of this paper is to present the method used to collect on-line real-time conversion measurements during an epoxy/fiberglass composite cure. For this purpose, temperature and ionic conductivity profiles during industrial moldings of a thick epoxy part were recorded. Corresponding conversion profiles were deducted from a previous empirically established correlation and discussed in terms of cure gradients as a function of the through-the-thickness location and of the cure cycle time.