The presence of xenobiotics in the environment always represents a risk for living organisms. Thus, there is a need to detect toxicity in the organism, and the concept of intoxication is related to specifi c organ alterations and clinical symptoms. Moreover, the relationship between the toxic levels within the organism and the toxic response is rather complex and has a diffi cult forecast because it depends on several factors, namely toxicokinetic and genetic factors. One of the methods to quantify the interaction with xenobiotics and its potential impact on living organisms, including the human being, is monitoring by the use of the so-called biomarkers. Biomarkers are used to detect the eff ects of pesticides before adverse clinical health eff ects occur. Pesticides and their metabolites are measured in biological samples, serum, fat, urine, blood, or breast milk by the usual analytical techniques. Biochemical responses to environmental chemicals provide a measure of toxic eff ect. A widely used biochemical biomarker, cholinesterase depression, measures exposure to organophosphorus and carbamate insecticides. Techniques that measure DNA damage (e.g., detection of DNA, protein and haemoglobin adducts) provide a powerful tool in measuring environmental eff ects. Determination of cytogenetic markers help in of monitoring populations occupationally or environmentally exposed to known or suspected mutagenic-carcinogenic agents. Thus suitable bioindicators, containing specifi c biomarkers hold the future trend of environmental monitoring