In the diagnosis and evaluation of progression of chronic open-angle glaucoma, a quantitative comparison of visual fields is important for which a knowledge of the spontaneous fluctuation of the visual field is essential. This study shows that in patients with glaucoma, the components of the short- and long-term fluctuation are substantially greater than in patients without the disease. Patients with suspected glaucoma show fluctuation in between, and all components of the fluctuation are greater in them than in normals and smaller than in patients with open-angle glaucoma.