The objectives of this assessment were: (1) to determine whether underground injection of hazardous wastes is an appropriate method of waste disposal in Illinois, and (2) to provide recommendations to the Illinois Legislature, the Illinois Legislative Council, the Illinois Governor1s Office, and Illinois state agencies concerning this disposal practice. Because the injection of nonhazardous wastes in Class I wells in Illinois governed by the same basic regulations as hazardous waste injection, nonhazardous Class I wells have been included in the study.