Heat Shock Protein 70 (HSP70) are generalist stress proteins expressed in response to numerous environmental stresses. However, the baselines of these constitutive proteins are still unknown in many organisms and in particular marine intertidal species such as the Pacific oyster, Crassostrea gigas. I demonstrate that levels of heat shock proteins (HSP) and other stress proteins (metallothioneins, MTs) quantified by ELISA, remained similar in gills, mantle and digestive gland between oysters inhabiting cold and hot sites. In contrast, endogenous HSPs and MTs levels in gonad changed significantly during gametogenesis. In female gonads, the constitutive form of HSP70 and the MTs increased from immature to mature stages (about more than 3-fold) and decreased after spawning. In male gonads, the same expression patterns were observed, whereas protein levels were lower and decreased once fully mature. I hypothesize that the high level of stress proteins in eggs may increase survival of oyster progeny