The knowledge on the contaminants agents’ bioaccumulation dynamics in bivalve tissues is important because shell fish consumption may represent a toxic risk to humans. By looking at the selective pressure to which the bivalve mollusks were submitted along their evolutionary process, a better understanding on bivalves as a biologic model for environmental contamination assessments can be achieved. The capacity to control toxic elements by bivalves is especially important to environment toxicology. Bivalves that are able to accumulate high contaminant levels with no apparent toxic effect exhibit special potential as “sentinel species”. Different strategies of metal distribution through the organs result in different bioaccumulations patterns in each organ/tissue. Along the last fifty years the bivalves have been widely used as environmental matrix, and their potentiality and limitations for environment toxicology are still under debate. In this review we intend to discuss the principles of bivalve’s applicability as a tool for environmental biomonitoring and the present paradigms and future perspectives of bivalves as a model in environment toxicology.