While we human beings, with our ingenuity, have been able to raise our general living standards to unprecedented levels, in the process we have also created an explosion of pollution problems. Today, we are confronted with toxic chemicals in the soil, air and water; destruction of stratospheric ozone; undesirable chemicals in our food; acid rain; indoor air pollution; deforestation and destruction of habitats, and potentially disastrous global climatic change. Meeting the challenges represented by these problems requires the strength of peoples and their governments, a multi-disciplinary approach and international goodwill and cooperation. The Fourth Symposium on Our Environment, held from May 21-23, 1990, represented part of our continuing efforts to contribute to the reduction, if not the solution of burgeoning pollution problems. The Symposium brought together scientists, industrialists and professionals in various disciplines to exchange ideas and expertise in dealing with environmental problems. It also helped to raise the level of awareness of the general public to the various environmental issues.