Recurrent Laryngeal Neuropathy is a performance limiting neurological condition that typically affects larger breed horses, such as Thoroughbreds and Draft-breed horses. The exact cause of the condition is unknown, however environmental and genetic factors both contribute to disease development. Affected horses loose the ability to maximally open the left side of the larynx during strenuous exercise, which limits the airflow in to the lungs leading to the poor performance. Unfortunately treatment options are limited to invasive surgical procedures which either permanently 'tying' the left larynx in an open position, or they totally ablate the left larynx. Complications from these surgeries can result in poor performance themselves as they include aspiration pneumonia, lower airway diseases, and even euthanasia if the surgery is not successful. The aim of this study is to try and elucidate underlying genetic risk factors for RLN, to help us understand what causes the condition and in order for a genetic test to be developed which could help owners to breed away from RLN.