['Large colon volvulus results in strangulating obstruction requiring surgical treatment. Duration of this disease prior to surgical treatment is likely to influence survival directly.', 'The primary objective of this study was to evaluate the influence of duration of large colon volvulus on patient survival to discharge. Relationships between other factors and survival following large colon volvulus were also examined.', 'Retrospective case analysis.', 'Medical records of Thoroughbred mares aged ≥2 years undergoing surgical treatment for large colon volvulus between 1 March 1986 and 28 February 2011 were reviewed. Multivariable logistic regression was used to identify influence of duration and other factors on survival to discharge.', 'Within the study period, 1039 surgeries were performed to correct large colon volvulus in 896 Thoroughbred mares. Median duration of colic signs prior to admission was 2\u2009h (interquartile range [IQR] 1-4\u2009h). Median time from admission to anaesthetic induction was 25\u2009min (IQR 15-45\u2009min). Median surgical time was 70\u2009min (IQR 55-85\u2009min). Primary surgical treatment was simple correction of the large colon volvulus followed by replacement of the colon. The overall survival to discharge was 88%. The final model identified risk factors significantly associated with survival and included colic duration prior to admission, packed cell volume at admission, surgery length, duration of hypotension while under anaesthesia, heart rate 48\u2009h post operatively, post operative manure consistency and days hospitalised.'] Does duration of disease influence survival to discharge of Thoroughbred mares with surgically treated large colon volvulus?