Summary Background Traveller’s diarrhoea (TD) is the most common infectious problem for travellers, and we lack effective ways of preventing it, apart from antibiotic prophylaxis. This study aims to quantify the risk reduction of a hypothetic TD vaccine Norwegian travellers are willing to pay for. Methods 1204 clients at Reiseklinikken responded to a questionnaire asking what level of effectiveness would be required of a hypothetical vaccine against TD costing US$65. Results 18.7% of the respondents would buy the vaccine even if it was only 20% effective. Among respondents older than 50 years, the proportion was 28.8%. Conclusions Our findings should encourage the development of vaccines and other preventive measures against travellers’ diarrhoea.