Objective. To obtain prevalence estimates of clinical features of obstructive sleep apnoea (OSA) and identify the dimensions of the public health problem requiring further investigation for an Australian population. Methods. The South Australian Health Omnibus Survey is an annual representative population survey of South Australians aged≥15 years, conducted via interviewer-administered questionnaire. In 2009, 3007 participants were asked the STOP-BANG instrument measure of obstructive sleep apnoea risk, which includes symptoms of loud snoring, frequent tiredness during daytime, observed apnoea, and high blood pressure (STOP), and measured body mass index, age, neck circumference and gender (BANG). Three or more positive response categorises a person at high risk for OSA. Results. Snoring was reported by 49.7% of adults. Tiredness after sleep more than 3 - 4 times per week was reported by 24.8%, and during wake-time by 27.7% of adults, with 8.8% reporting having fallen asleep while driving. Over half of the surveyed men (57.1%, n≤566) and 19.3% (n≤269) of the women were classified at high-risk of OSA with the STOP-BANG measure. In multivariable models, high risk was associated with less education, lower income, and residence in a regional rather than metropolitan area. Conclusion. The high prevalence of adults at risk for OSA suggests that the capacity currently available within the healthcare system to investigate and diagnose OSA is likely to be inadequate, particularly outside urban areas. This highlights an important public health problem that requires further detailed study and trials of new models of care. What is known about the topic? Obstructive sleep apnoea (OSA) is associated with obesity, and although it is associated with significant morbidity and mortality there is no simple clinical test for this condition. While the prevalence of snoring or sleepiness is reported to be high and increasing with obesity, there is little recent information on how many adults report combinations of frequent sleep-related breathing abnormalities, unsatisfactory sleep, or unexplained daytime sleepiness, that justify further investigation with tests such as polysomnography that require considerable health service investment. What does this paper add? In a representative adult population sample of 3007 adults, 27.8% were classified at high risk of OSA with a validated screening tool that uses symptoms and body measurements (STOP-BANG). Risk was greater with lower income and education, and residence outside of metropolitan areas. What are the implications for practitioners? Clinicians need to be aware that over a quarter of adults may need investigation for OSA, and should adopt an active approach to identifying people at risk. Health services and policy makers need to plan for this problem, and innovative approaches to provision of investigation and management need to be trialled.