Summary Reasons for performing study: Welfare concerns over the reasons for interruption or termination of a sporting career in horses have been expressed. Objectives: To study the career of competition horses and factors that influence career length. Methods: In 2004, 46,576 rider‐horse combinations were registered with the Dutch National Equestrian Federation (KNHS) in dressage, show jumping, eventing and endurance. From this population, approximately 1% of horses in each discipline were selected at random and all recorded competition data from the KNHS registration system collected and supplemented by detailed rider/owner telephone enquiry, carried out in July 2009. Results: A total of 520 horses were included aged 7.1 ± 3.2 years; endurance horses were on average slightly older than horses in the other 3 disciplines. A total of 334 horses (64.2%) ended their competition career with their initial rider during the study period; the mean total career time was 3.8 ± 2.8 years. Reasons for this included being sold on (51.5%), veterinary reasons (23.9%), being used for breeding (8.7%), changing to a recreational career (8.1%), rider‐related issues (6.3%) and retirement (1.5%). No follow‐up was available for horses sold. Orthopaedic problems accounted for the majority of the veterinary career‐ending decisions (63.7%). A total of 385 horses (74.0%) had one or more career breaks; main reasons were rider‐related issues (39.2%), others included temporary withdrawal from competition (21.6%), veterinary problems (21.8%), breeding (9.1%) and miscellaneous (8.3%). Conclusions: Veterinary reasons for career breaks or termination of career accounted for 21.8 and 23.9% over the period investigated. They formed the second reason (after selling) why horses stopped competing with their initial rider/owner. Veterinary reasons were the third important cause for a temporary career break. Potential relevance: Further in depth research of the reasons for interruption or termination of an equine career may be useful for the ...