The fact that members of the genus Trillium are quite variable is well borne out when one notes the number of reports of variations and teratological conditions in the literature. Such conditions make it important that more detailed critical study be made of members of the genus from the standpoint of their distribution and variation in smaller areas. Studies of the species occurring in wider areas were made by Gleason (19) and Gates (18). More detailed study of particular species in more restricted areas is of considerable value in adding light to the problem of species relationship and delimitation. Such a study was made for North and South Carolina by Peattie (26). The present paper is a similar attempt for the state of Indiana.