An investigation was carried out to modify the fracture toughness of cured diglycidyl ether of bisphenol-A (DGEBA) resin networks with amine functional chloroaniline acetaldehyde condensate (AFCAC) as toughening agent. The resulting networks displayed significantly improved fracture toughness. The AFCAC was synthesized by the condensation reaction of chloroaniline and acetaldehyde in the acid medium (pH-4) and characterized by FTIR and NMR spectroscopy, elemental analysis, viscosity measurements, and mole of primary and secondary amine analysis. The DGEBA and AFCAC were molecularly miscible but developed a two-phase micro-structure upon network formation. Epoxy/AFCAC compositions were systematically varied to study the effect of concentration on the impact, adhesive, tensile, and flexural properties of modified networks. The dynamic mechanical analysis and scanning electron microscopy studies showed two-phase morphology in the cured networks where AFCAC particles were dispersed. The AFCAC-modified epoxy network was thermally stable LIP to around 338 degrees C. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3717-3726, 2008