This volume explores the applicability of bioassays and bioindicators as tools for evaluating the effects of dredged sediments on the marine ecosystem. Waterways and harbors in delta areas must be dredged regularly to remove sediments which might otherwise block shipping routes, and hundreds of millions of tonnes of sediment are removed each year worldwide. Besides containing a relatively high amount of organic matter, these sediments also contain a complex mixture of chemicals, many of which are toxic to some degree. These cocktails of compounds in dredged material, and their effects on the environment, are as yet inadequately measured and assessed. One approach to identifying the toxicity of the mixture of unmeasured chemicals present in dredged material is by effect-based bioassays, quantifying the effect of a whole mixture rather than that of each compound. This study analyses the application of bioassays and develops a rationale for their inclusion in hazard, risk and impact assessment of dredged sediments. It also establishes a comprehensive set of bioassays and markers to assist this process. Aspects covered include: the predictability of in vitro and in vivo bioassays and markers, the applicability of the DR-CALUX bioassay in the licensing system, the optimization of an in vivo bioassay with cultured heart urchins (E.cordatum) and a site-specific assessment of TBT originating from anti-fouling paint in marine and harbor sediments. This book is an important contribution to the improved understanding vital to minimize the risks associated with the disposal of dredged materials.