The effects of Skydrol 500B-4 on the cure characteristics of a diaminodiphenyl sulfone-crosslinked tetraglycidyl 4,4’-diaminodiphenyl methane resin were investigated by the use of calorimetric, rheological, and gravimetric analyses. The chemical system studied was I.C.I’s Fiberite 934 epoxy resin. The kinetics of cure were determined by the use of differential scanning calorimetry. The results indicated that the hydraulic fluid did not alter the kinetic parameters (E(a), A, k, t(1/2)) of the crosslinking reactions but diminished the overall heat of the reaction. Gelation and vitrification of the growing networks were observed by the use of dynamic mechanical thermal analysis. The results showed that Skydrol had a marked effect on reactions transpiring within the gel. Thermogravimetric analysis (TGA) was used to estimate the extent of Skydrol elimination during cure. TGA curves indicated that a significant degree of interaction occurred between the hydraulic fluid and the component(s) of the resin.