In the present work we have studied the effects on survival as well as histopathological and histochemical alterations on the digestive gland of the Portuguese oyster (Crassostrea angulata, Lmk.) induced by acute action of the anionic tensioactive Sodium Dodecyl Sulphate (SDS) at different concentrations (50, 100, 200 and 400 mg/L). Firstly, the LC 50 at 96 h was found to be 136 mg/L SDS. Secondly we calculated the exposure time required for 50% mortality of the specimens exposed to different concentrations, and thirdly we examined histopathological alterations (degenerative processes ranging from inflammatory responses to extreme vacuolation) and histochemical changes in the distribution of carbohydrates and proteins that appeared at each employed concentration. The degree of these alterations and the effects on survival were dependent upon the SDS concentration. The above established modifications indicate that exposure to SDS has a detrimental effect on oyster digestive gland, perturbing metabolic and nutritional functions, what may have some influence on oyster survival.