This didactic unit has the same name as the descriptor that it seeks to cover. The Toxicology and Ecotoxicology assay methods most used and required in the current legislation will be described. All this without forgetting the existence of alternative methods to the use of experimental animals and the need for their development and validation. The contents of this didactic unit are reinforced with laboratory practices, where the two most common types of ecotoxicological assays (Daphnia magna mobility test and luminescent bacteria) will be performed as well as a green algae inhibition test. A Ames mutagenicity assay will also be performed in liquid format.