Reasons for performing study: Equine grass sickness (EGS) remains a frequently fatal disease of equids in Great Britain (GB). The first nationwide surveillance scheme for EGS was developed to obtain information on the occurrence of EGS and to help facilitate future proposed intervention studies, such as vaccine trials. Objectives: To collect both retrospective and prospective data on cases of EGS occurring in GB since 2000 and to assess potential risk factors for categories of EGS and survival after chronic EGS. Methods: Prospective data were collected using a nationwide surveillance scheme for EGS that was developed and initiated in 2007. Data were collected by means of postal and online questionnaires documenting both retrospective premises-level and prospective case-level information. Data on outcomes of EGS category and survival after chronic grass sickness (CGS) were analysed using univariable logistic regression. Results: Descriptive data for 1410 EGS cases occurring in GB in the decade between the beginning of 2000 and the end of 2009 are presented. Univariable logistic regression analyses identified that CGS cases in Scotland were significantly more likely to survive than those occurring elsewhere in GB. There was no relationship between case details and the category of EGS or the outcome among CGS cases. Conclusions: EGS affected equids throughout England, Scotland and Wales. Although an overall average of 141 cases were reported to the nationwide surveillance scheme annually, this number of cases was not consistent between years. Around 50% of CGS cases survived, although regional differences in survival rates existed, probably due to variation in expertise of care and/or disease severity. Potential relevance: This study provides information on the spatiotemporal occurrence of EGS in GB during the last decade. Data from the nationwide surveillance scheme can be used in developing protocols for future intervention studies such as Clostridium botulinum vaccine trials.