The volume contains the main papers presented at the 1994 EUROTOX Congress, Basel, Switzerland, August 21-24, 1994. Toxicology has become a less descriptive science because more importance has been placed on the mechanisms underlying toxic effects. This is reflected in symposia and workshops devoted to species differences in organ toxicity, receptor-mediated toxicity and stereochemical effects of xenobiotics. Recent progress in the fields of immunotoxicology, ecotoxicology, and neurotoxicology is highlighted and documented together with the present discussion on harmonized regulatory guidelines.