Bisphenol-A (BPA) is a well-known xenoestrogen in mammalian systems that can affect reproduction also in aquatic organisms. In this work the possible effects of BPA were investigated in the hepatopancreas of the bivalve mollusc Mytilus galloprovincialis: mussels were injected with different amounts of BPA (3-60ng/g dw tissue) and tissues sampled at 24h post-injection. Expression of different Mytilus genes was evaluated by RT-Q-PCR: BPA exposure increased the expression of MeER2 and induced downregulation of antioxidant genes, catalase and metallothioneins. Moreover, BPA induced changes in activity of catalase, GSH transferase (GST) and GSSG reductase (GSR), and in total glutathione content. A decrease in lysosomal membrane stability and increased neutral lipid accumulation were also observed. The results were compared with those obtained with similar concentrations of 17beta-estradiol. These data demonstrate that BPA can alter gene expression, activities of enzymes involved in redox balance, and lysosomal function in molluscan hepatopancreas, a tissue involved in the control of metabolism and gamete maturation. Overall, these data indicate that BPA, at environmentally relevant concentrations, can have both estrogen-like and distinct effects in invertebrates like in vertebrates.