Primary open-angle glaucoma (POAG) is one of the leading causes of blindness worldwide. Patients are usually asymptomatic until severe anatomic and functional damage occurs. Visual field examination is important in managing glaucoma patients, especially in the treatment and follow-up of moderate to advanced cases. This study was designed to investigate the patterns of automated visual field defects in POAG. We studied 296 POAG patients from the Glaucoma Clinic of the National Taiwan University Hospital from January 1986 to June 1996. The perimetry was performed using the Octopus program 32 or 38, or Humphrey program 30-2, and the results were analyzed according to the Glaucoma Hemifield Test design. The depth and frequency of locations of visual field defects were computed, and stratified by age and intraocular pressure (IOP). The results suggested that the most frequently affected locations in POAG were paracentral areas, while the deepest scotoma appeared in the upper and lower nasal areas. Patients with IOP higher than 25 mmHg or older than 50 years had higher mean sensitivity losses in both superior and inferior hemifields. The results of this study revealed the patterns of automated visual field defects in POAG may be a useful guide for the management of POAG patients.