Although the gingival index and sulcus bleeding index have been widely used as indicators of periodontal status, there is some disagreement among investigators as to their meaning and significance. A clinical study was undertaken to monitor the occurrence of gingival bleeding, oedema, and change in colour in subjects with and without periodontal disease, and it was found that the combinations of these clinical symptoms often did not correspond exactly with an index score. It is therefore suggested that any study of periodontal disease should be based on fundamental criteria, such as bleeding or oedema, rather than on composite indices.