The NCI Clearinghouse for Environmental Carcinogens acts as an advisory body to the Carcinogenesis Testing Program of that Institute. It consists of 30 members, from academic institutions, labour organizations, consumer groups and industry. They are divided into three groups: the Chemical Selection group establishes priorities for compounds to be tested; the Experimental Design group decides on the test procedures and parameters to be used; and the Data Evaluation/Risk Assessment group review data from completed tests, for deficiencies in experimental design or conduct, the nature of the lesions produced and the statistical analysis of the results, and gives a critical opinion of the test.