The purpose of this study was to determine the prevalence of glaucoma in Ponza, Italy. The design was a population-based prevalence survey of residents of Ponza aged 40 years or older. There were 1,296 official residents identified by a house-to-house census, of whom 1,226 were identified as eligible for the study. Of these, 1,034 individuals (449 males and 585 females), or 84.3% of the eligible population, participated in the ophthalmological examination. A two-stage method was adopted to identify cases of glaucoma. All subjects underwent a standardized initial examination. Glaucoma suspects and 50% of non-suspects were referred to a definitive examination which included visual field testing. Patients were defined as glaucoma cases if they presented abnormal visual fields and at least one of the following: high 10P, large or asymmetric cup-to-disc ratio. In addition to typical glaucomatous visual field defects such as paracentral scotoma, nasal step, arcuate scotoma and temporal and/or central islands fields, a visual field defect was identified as a decrease in sensitivity greater than 6 db in at least one location of the central 10 degrees, two locations of the central 20 degrees or three locations of the central 30 degrees. Prevalence rates of 2.51% of Primary Open Angle Glaucoma (1.72%-3.66%, CI 95%), 0.97% of Primary Closed Angle Glaucoma (0.53%-1.77%, CI 95%) and 0.29% of secondary glaucoma were found. Moreover, 2.13% of probable POAG (1.41%-3.20%, CI 95%) and 6.00% of High Intraocular Pressure (4.71%-7.61%, CI 95%) were found. The prevalence rates of POAG found in the Ponza Ophthalmological Survey are consistent with the results of other studies. Minor differences are most likely due to the different criteria adopted in the assessment of glaucomatous visual field damage.