In a remote site in eastern Idaho, now known as the Idaho National Engineering and Environmental Laboratory (INEEL) Site, the U.S. Government established a facility to test-fire naval gunnery during World War II. The mission after the war switched to development and demonstration of nuclear technology. For more than 50 yr, the site has been devoted to nuclear energy research. Because of the remote location of the site west of Idaho Falls, ID, wastes containing radioactive and hazardous materials were disposed to the subsurface. It was felt that any disposed materials would not travel downward through the vadose zone, which is 100 to 300 m thick, to the underlying Snake River Aquifer. However, some materials have traveled through the thick vadose zone and contaminated the aquifer. Other wastes were injected directly into the aquifer. To provide a general background for papers in this special issue of Vadose Zone Journal on research at the INEEL, we give a brief historical perspective of work conducted at the INEEL Site west of Idaho Falls and associated subsurface contamination issues. We furthermore give an overview of the research papers presented in this special issue.