In view of the growing public debate on possible health effects of dioxins, the WHO Regional Office for Europe organized a Consultation to review the available research data on exposure levels and health effects, and, based on a comprehensive toxicological evaluation, to develop guidelines for Tolerable Daily Intake (TDI) of PCDDs and PCDFs. Since there are about 200 dioxin isomers, it was decided to develop guidelines for a TDI based on ail evaluation of human health risks of 2,3,7,8-tetrachlorodibenzodioxin (2,3,7,8-TCDD), which is the most studied and most toxic isomer in this mixture of chemicals. The consultation also developed guidelines for risk management, with emphasis on the main sources of food contamination.