Samples of surface water were collected and analyzed by the Illinois Environmental Protection Agency and its predecessor, the Stream Pollution Control Bureau of the Illinois Department of Public Health. The results for the period 1958 to 1974 are presented in tabular form and the history of sampling and analytical methods are summarized. Stream discharge data from records of the U.S. Geological Survey are included for all sites where saples were collected at gaging stations or near enough that reliable discharge estimates could be made. The report is contained in three volumes. This volume (Volume III) includes Ohio River tributaries and Mississippi River tributaries south of Illinois River basin. (See also W78-10034 and W78-10035)