The major causes of cancer in the developed countries are now thought to be environmental or man-made factors. Because most carcinogens are also mutagens, the detection and identification of muta/carcinogens to humans seem to be very important in the environmental sciences. We describe here, i) in vitro and in vivo short-term assays for muta/carcinogens in the environment, ii) possible method for monitoring human exposure to muta/carcinogens, and iii) some trials for estimating human risk for the development of cancers due to environmental mutagens.