The present work discusses two main environmental applications of biosorption and bioaccumulation processes. The first is environmental biomonitoring performed by living organisms. The property that is used here is that the level of a given contaminant in biological tissues is related to the concentration of this substance in the environment. This is expressed by the assessment of bioaccumulation factors. This book reports examples of the application of human hair and consumable tissues of animals, and various parts of plants (green parts as well as wood) in environmental pollution monitoring. Biosorption as well as bioaccumulation can find an application in removal of contaminants from aqueous solutions. Biosorption by different materials of plant (microalgal biomass, aquatic plants, plant leaves, straw, grass) and animal origin (eggshells, bones) can be applied in industrial wastewater treatment processes. Also, bioaccumulation by aquatic organisms: microalgae, macroalgae and aquatic plants in metal ions removal from effluents can be used to bind metal ions simultaneously with nutrients. An attempt to make the processes predictable is discussed here, including screening for good biosorbents/bioaccumulators, determining biosorption and bioaccumulation capacity as well as bioavailability as the function of the concentration of metals in the environment in which an organism is present, together with growth requirements, mathematical modelling, carrying out processes at different process conditions. This should constitute the basis for the assessment of standardized procedures, in the design of biosorption or bioaccumulation treatment plants and for environmental biomonitoring.