Gaucher disease (GD) is a lysosomal storage disorder, due to glucosylceramide (GlcCer) accumulation in several body tissues, which causes cellular failure by yet unidentified mechanisms. Several evidence indicates that GD pathogenesis is associated to an impairment in intracellular redox state. In fibroblast primary cultures, reactive oxygen species (ROS) levels and protein carbonyl content resulted significantly increased in GD patients compared to healthy donors, suggesting that GD cells, facing a condition of chronic oxidative stress, have evolved an adaptive response to survive. The ROS rise is probably due to NAD(P)H oxidase activity, being inhibited by the treatment with diphenylene iodonium chloride. Interestingly, GD cells are more sensitive to H₂O₂ induced cell death, suggesting a dysregulation in the adaptive response to oxidative stress in which APE1/Ref‐1 plays a central role. We found that the cytoplasmic amounts of APE1/Ref‐1 protein were significantly higher in GD fibroblasts with respect to controls, and that GD cells failed to upregulate its expression upon H₂O₂ treatment. Both ROS and APE1/Ref‐1 increases are due to GlcCer accumulation, being prevented by treatment of GD fibroblasts with Cerezyme® and induced in healthy fibroblasts treated with conduritol‐β‐epoxide. These data, suggesting that GD cells display an impairment in the cellular redox state and in the adaptive cellular response to oxidative stress, may open new perspectives in the comprehension of GD pathogenesis. J. Cell. Physiol. 212: 223–235, 2007. © 2007 Wiley‐Liss, Inc.