Endocrine toxicology has become an increasingly important research area since the extent of adverse effects by endocrine disrupting chemicals, or endocrine disruptors, was realized. Increasing incidence of endocrine-related cancers and other endocrine diseases is strongly pointing to environmental causes. Identification of endocrine affecting properties of a vast number of chemicals provides a good reason to hypothesize that they may contribute to our disease burden. Results of studies in experimental animals support findings in epidemiological studies that by themselves can only suggest associations. With a weight of evidence approach we can determine whether a compound is an endocrine disruptor, which leads to its regulation to protect our health.