These two volumes contain the papers presented at a North Atlantic Treaty Organization (NATO) Advanced Study Institute held on September 22-28, 1979 in Monte Carlo, Monaco. The conference was entitled In Vitro Toxicity Testing of Environmental Agents: Current and Future Possibilities. This international conference presented an opportunity for the participants to exchange informa tion and ideas on the current approaches (both scientific and po litical) for toxic assessment of environmental agents. The poten tial health effects of these compounds as well as future needs in the environmental research field were discussed. The scientific content of the conference seminars included an overview of the various cellular, subcellular, organ, animal, and genetic systems which have been used to assess the health effects of environmental agents. The scientific principles behind short term assays and an evaluation of their applicability to health effects monitoring and analysis were investigated. Included among major topics were: (1) the biochemistry and pharmacology of selected environmental agents; (2) molecular mechanisms of car cinogenesis, mutagenesis, and transformation; (3) bacterial muta genesis and toxicity; (4) mammalian cell mutagenesis, toxicity, and transformation; (5) in vitro carcinogens and mutagens; (6) teratogenic and other developmental toxic effects; and (7) the development of short-term neuro-behavioral toxicity assays.