To examine how individual surfing behaviour affects the development of external auditory canal exostosis and to produce a model to predict exostosis severity. A standardised questionnaire was completed and each participant underwent an otoscopic examination. Surfers were recruited from August to October 2011 from surfing competitions and from colleges in the South West of England. 207 surfers were included, 53 % had evidence of external auditory canal; exostosis: grade 1, 23%; grade 2, 16%, grade 3, 16%. This risk of exostosis significantly increased with (1) surfing for 6 or more years, (2) surfing in the winter months, (3) surfing five or more times per month in the winter and (4) reported ear symptoms. Interestingly, participation in other water sports and wearing earplugs or a hood reduced the risk of developing exostosis. Surfers who surf in England are at significant risk of exostosis. A probability model was designed, incorporating different surfing behaviours and ear symptoms, the first of its kind in exostosis research. This model will be a useful tool for raising awareness of external ear canal exostosis in the surfing community and in assessing individual need for surgical intervention.