Peter Matthiessen is the sole, self-employed staff member of the Peter Matthiessen ecotoxicology consultancy. This consultancy has been in continuous operation since 2006, and has a wide range of clients in government, NGOs and industry. The consultancy has tended to specialise in the provision of advice in the field of endocrine disruption, but has also been directly involved in research on the effects of various endocrine disrupters (EDs) on fish and amphibians. A particular speciality of the consultancy has been the development and validation of new ecotoxicity test methods for endocrine disruptors.