Since the first edition of 1999, 34 additional species of plants have been recognized in Illinois. Some are from recent field work, some are from more thorough searches of herbaria, and others are due to different taxonomic philosophies. For each of the 159 species of Carex in Illinois, there is a full illustration showing the habit of the plant and close-ups of various vegetative and reproductive structures that are crucial for the identification of the individual species. There is also a complete description of each species as well as a discussion of the nomenclature and habitats. Range maps show the county distribution of each species in Illinois. A detailed key is provided for identification of the species.