BackgroundSexually transmissible infections (STIs) continue to rise in people aged 15–29 in New South Wales (NSW), Australia (≥30,000 chlamydia (CT) notifications annually). However, STI testing rates are low and stigma remains about STI and testing.MethodsDown to Test is a social marketing program targeting high-risk young people to improve attitudes and social norms for condom use and STI testing - facilitators for healthy sexual behaviour. The program includes information, blogs & forums at playsafe.health.nsw.gov.au and involves online marketing and face-to-face, peer-led music festival activations – an incentivised VIP area (clean toilets, phone charging, glitter bar, condoms) and access with a urine specimen for CT testing. Market segmentation research of values, attitudes and behaviours identified 2 high-risk groups of young people -‘experienced sex positive’ and ‘dominant risk-takers’. Program strategies and incentives were developed with these groups who identified peers to also help deliver the program.ResultsBetween 9/2017 and 12/2018, 5783/124,000 (5%) young people registered for the VIP area during 7 NSW festivals. 189/5416 (3.5%) tested CT+. All CT- received SMS, 93% CT+ were informed & 75% confirmed treatment. Digital engagement metrics: 863,931 impressions, 1% Cut Through Rate for linked advertisements, 0.05% social engagement, and 5,000 peer educator conversations with campaign recall increase of 25%. Pre & post-intervention surveys showed increased social norms for STI testing (24% increase), positive attitudes (26%), and intention to STI test in the next 12 months (32%). Over 80% of participants were within the two high-risk groups.ConclusionDown to Test successfully engaged high risk young people attending music festivals and improved healthy sexual behaviour facilitators. Applying segmentation research and engaging the identified groups improved the likelihood of success by better targeting the activations. Broad reach across NSW was maximised by using festivals in a variety of locations. The program is adaptable to other locations.DisclosureNo significant relationships.