Knowledge about and experience of sexually transmissible infections in a representative sample of adults: the Second Australian Study of Health and Relationships Andrew E. Grulich A,I , Richard O. de Visser B , Paul B. Badcock C,G , Anthony M. A. Smith C,H , Juliet Richters D , Chris Rissel E and Judy M. Simpson F A Kirby Institute, University of New South Wales, Sydney, NSW 2052, Australia. B School of Psychology, Pevensey 1, University of Sussex, Falmer BN1 9QH, UK. C Australian Research Centre in Sex, Health and Society, La Trobe University, 215 Franklin Street, Melbourne, Vic. 3000, Australia. D School of Public Health and Community Medicine, University of New South Wales, Sydney, NSW 2052, Australia. E Sydney School of Public Health, Charles Perkins Centre (D17), University of Sydney, Sydney, NSW 2006, Australia. F Sydney School of Public Health, Edward Ford Building (A27), University of Sydney, Sydney, NSW 2006, Australia. G Present address: Centre for Youth Mental Health, University of Melbourne, Orygen Youth Health Research Centre, 35 Poplar Road, Parkville, Vic. 3052, Australia. H Deceased. I Corresponding author. Email: agrulich@kirby.unsw.edu.au Abstract. Background: Sexually transmissible infections (STIs) present a substantial public health burden, and are related to modifiable sexual behaviours. Methods: Computer-assisted telephone interviews were completed by a population-representative sample of 20 094 men and women aged 16–69 years. The overall participation rate among eligible people was 66.2%. Respondents were asked questions regarding their knowledge about, self-reported history of, and testing for STIs. Results: STI knowledge was better in women, the young, people of higher socioeconomic status, those with a variety of indicators of being at high STI risk and those with a history of receiving sex education in school. Approximately one in six men and women reported a lifetime history of an STI. A history of STI testing in the last year was reported by ~one in six (17%) women and one in eight men (13%) and higher rates of testing in women were reported in most high-risk groups. The highest rates of STI testing (61%) and HIV testing (89%) were reported in homosexual men. Conclusion: Knowledge of STI-related health consequences and transmission is improving in Australians, and rates of STI testing were relatively high but were higher in women than in men. Further increases in testing rates in both sexes will be required to facilitate the early diagnosis and treatment of STIs, which is a cornerstone of STI control. Received 25 June 2014, accepted 19 August 2014, published online฀7฀November฀2014 Introduction The World Health Organization has estimated that ~500 million people develop a curable sexually transmissible infection (STI) annually 1 and an even greater number are estimated to have a viral STI at any point in time. 2 Given the very high prevalence of some STIs, particularly human papillomavirus (HPV), most sexually active people will acquire a STI at some time in their lives, although most of these are asymptomatic. Incidence is highest in the young, 3 who have higher rates of partner change. Although a large majority of STIs are asymptomatic, a variety of adverse health outcomes may occur, including genital and systemic symptoms and accompanying psychological distress, pregnancy complications, cancer and infertility. 2 Several STIs may also increase the risk of acquiring and transmitting HIV. 4 The total direct cost of STIs diagnosed in 2008 in the US was estimated to be $15.6 billion. 5 In recent years, increasing incidence of many STIs has been described in many high-income settings. For example, in Australia, in the 5 years leading up to 2012, age-standardised rates of diagnosis of HIV, chlamydia, gonorrhoea and infectious syphilis all increased, by 15%, 34%, 68% and 10% respectively. 6 In Europe during the period 1990–2009, annual diagnoses of chlamydia continuously increased. 7 Although the overall trend for gonorrhoea and syphilis was slightly CSIRO PUBLISHING Sexual Health, 2014, 11, 481–494 http://dx.doi.org/10.1071/SH14121 Journal compilation Ó CSIRO 2014 www.publish.csiro.au/journals/sh