This document specifies a method for determining the effects of chemical and aqueous samples on the embryo-larval development of marine bivalves. It allows the determination of the concentration levels that result in an abnormality in embryo-larval development. This test is suitable for salinity ranges between 20 and 40 for mussels and between 25 and 35 for oysters. This method applies to - chemical substances and preparations; - marine and brackish waters; - streams and aqueous effluents (urban, agricultural, industrial effluents, etc.) as long as the salinity is adjusted and/or dilution is limited so that the aforementioned salinity ranges are respected; - aqueous extracts (pore water, elutriates, eluates, and leachates) from sediments and petroleum products, and - samples of contaminated sediment or dredged material.