ABSTRACT The Iroquois Woods Nature Preserve, located just south of Aroma Park, Kankakee County, is in the Kankakee Sand Area of northeastern Illinois. Three relatively distinct topographic zones exist within the preserve (low terrace, shallow depression, high sand terrace). The forest overstory in all three zones, however, is very similar with most of the same species occurring in each zone, but in different densities. These natural communities are probably due to elevation, distance from the river, soil moisture, and erosion due to flooding events. In the low terrace (mesic sand forest), located near the edge of the Iroquois River channel, Quercus rubra, Tilia americana, Ulmus rubra, Aesculus glabra, and Q. macrocarpa dominate, with the oaks in the larger diameter class. In the shallow depression (wet-mesic sand forest) behind the low terrace Quercus bicolor dominated with 50 stems/ha and accounted for almost half of the total basal area. Tilia americana and U. americana were second and third in importance due to the large number of small diameter individuals. East of the depression was a high sand terrace (dry-mesic sand forest) dominated by Q. alba followed by U. americana, Q. velutina, Prunus serotina, and Q. rubra. This preserve contains one of the few examples of high quality mesic sand forests in the state, but oak regeneration is limited, and shade-tolerant species are becoming more abundant.