Reasons for performing the study: There have been no reports of the efficacy of thermocautery of the soft palate (TSP) assessed objectively as a treatment of intermittent dorsal displacement of the soft palate (DDSP).Objective: To compare: racing performance of horses that underwent thermocautery of the soft palate with matched controls; and 'Racing Post ratings' (RPR) with prize money won (RE) and a performance index (PI) for each of the horses in the study.Hypothesis: Thermocautery of the soft palate has no beneficial effect on racing performance and the 3 measures of performance are significantly related.Methods: The inclusion criteria were fulfilled by 110 horses and each was matched with 2 controls. Changes in performance were compared statistically. RPR, RE and PI were analysed using a regression model.Results: The percentage of horses that improved in performance following the procedure was 28'51% for the 3 measures of performance, compared to 21'53% for the matched controls. There was no significant effect of the procedure on the changes in RPR or RE. There was a significant effect of the procedure on the change in PI (P = 0.015) with more treated horses achieving an improved PI and fewer acquiring a worse PI than matched control horses. The measures of performance showed significant correlation.Conclusions: Thermocautery of the soft palate alone may not be the most efficacious treatment of DDSP.Potential relevance: Production of a reliable measure of racehorse performance may be possible.