IntroductionSyphilis incidence is rising among gay, bisexual and other men who have sex with men (GBMSM). To improve early health-seeking behaviour, we developed an online syphilis symptom score tool for GBMSM to self-identify a higher likelihood of infectious syphilis and promoted its use via an online and offline awareness campaign.MethodsFrom October 2018 through September 2019, a dedicated website on syphilis including the online symptom score tool was promoted. The reach of the campaign was measured by website metrics and the completion of the self-assessment tool. The impact of the campaign was assessed by comparing the monthly number of syphilis serology tests and the percentages of infectious syphilis diagnoses at the Centre for Sexual Health (CSH) in Amsterdam between three periods: 12 months preceding, 12 months during and 6 months after the campaign.ResultsDuring the campaign, 20 341 visitors viewed the website. A total of 13 499 (66.4%) visitors started the self-assessment algorithm, and 11 626 (86.1%) completed it. Prior to the campaign, the mean number of syphilis tests per month was 1650 compared with 1806 per month during the campaign (p=0.02). In the 6 months after the campaign, the mean number of tests per month was 1798 (compared with the period of the campaign, p=0.94). Prior to the campaign, the percentage of infectious syphilis diagnoses was 2.5% compared with 3.0% during the campaign (p=0.009). The percentage of infectious syphilis diagnoses in the 6 months after the campaign was 2.2% (p<0.0001 compared with the period of the campaign, and p=0.045, compared with the period prior to the campaign).ConclusionsAlthough we did not find definite proof of a (sustained) effect, syphilis symptoms awareness campaigns deserve further evaluation and improvements to help those suspected of syphilis to get tested.