The report is a compilation of lake monitoring data for 37 lakes in the Northeastern Illinois Region (Cook, DuPage, Kane, Lake, McHenry, and Will Counties). A statewide summary (Hawes, 1987) is also available which provides information for all 127 lakes in the 1986 Volunteer Lake Monitoring Program (VLMP. Section 2 of the report provides a summary of regional results, including a discussion of lake characteristics and volunteer participation, and a ranking of lakes on a regional basis. Section 3 contains individual lake summaries for those VLMP lakes that were monitored nine or more sampling periods during the 1986 season. For each lake, transparency and field observations data are presented and discussed in terms of comparison to other lakes. Section 4 includes individual lake data (in tabular and graphic form) for those VLMP lakes in the region which were monitored less than nine sampling periods during the 1986 season.