While toxicity testing procedures and hazard assessment approaches have been published in past decades, many are wanting in detail for users to fully understand or reproduce successfully. Small-scale Freshwater Toxicity Investigations (Volumes 1 and 2) responds to this need by providing comprehensive information on biological testing which is normally scattered and difficult to find. In Volume 1, 15 chapters on toxicity tests are described in great detail by way of a homogeneous structure that all contributors had to follow. These comprehensive texts allow readers to be informed of relevant information (background, theory, practice) linked to each bioassay. Hence, book contents can be used both for technology transfer purposes (e.g., classroom or workshop courses) and to undertake practical toxicity testing (e.g., in a private, public or university laboratory). In Volume 2, 11 chapters on hazard assessment schemes are described in great detail by way of a homogeneous structure that all contributors had to follow. These comprehensive texts allow readers to know the different approaches/strategies, based on applying batteries of bioassays, that are being used internationally to assess the toxic potential of complex environmental media (e.g., effluents, sediments) impacted by chemical contamination stemming from human activities.