Aim. To describe the prevalence of and risk factors for pterygium in a population based sample of residents of the Australian state of Victoria who were aged 40 years and older. Methods. The strata comprised nine randomly selected clusters from the Melbourne statistical division, 14 nursing homes randomly selected from the nursing homes within a 5 kilometre radius of the nine Melbourne clusters, and four randomly selected clusters from rural Victoria. Pterygium was measured in millimetres from the tip to the middle of the base. During an interview, people were queried about previous ocular surgery, including surgical removal of pterygium, and their lifetime exposure to sunlight. Results. 5147 people participated. They ranged in age from 40 to 101 years and 2850 (55.4%) were female. Only one person in the Melbourne cohort reported previous pterygium surgery, and seven rural residents reported previous surgery; this information was unavailable for the nursing home residents. Pterygium was present upon clinical examination in 39 (1.2%) of the 3229 Melbourne residents who had the clinical examination, six (1.7%) of the nursing home residents, and 96 (6.7%) of the rural residents. The overall weighted population rate in the population was 2.83% (95% CL 2.35, 3.31). The independent risk factors for pterygium were found to be age (OR = 1.23, 95% CL = 1.06, 1.44), male sex (OR = 2.02, 95% CL = 1.35, 3.03), rural residence (OR = 5.28, 95% CL = 3.56, 7.84), and lifetime ocular sun exposure (OR = 1.63, 95% CL = 1.18, 2.25). The attributable risk of sunlight and pterygium was 43.6% (95% CL = 42.7, 44.6). The result was the same when ocular UV-B exposure was substituted in the model for broad band sun exposure. Conclusion. Pterygium is a significant public health problem in rural areas, primarily as a result of ocular sun exposure.