Do stable personnel agree on the personality characteristics of horses in their care? Working independently and under experimenter supervision, nine stable personnel rated the personality characteristics of each of 10 individual horses using a questionnaire adapted from the NEO-PI-FFI of Costa and McCrae [Costa Jr., P. T. & McCrae, R. R. (1992) Revised NEO Personality Inventory (NEO-PI-R) and NEO Five Factor Inventory (NEO-FFI) professional manual. Odessa FL: Psychological Assessment Resources]. Raters achieved high inter-correlations in the ranking of the horses for all the Big Five dimensions, with the strongest agreement being achieved for Neuroticism and Extraversion. While previous research has demonstrated individual differences reminiscent of human personality characteristics, relatively few studies have explicitly used a human personality inventory for application to another species. It is also relatively rare for raters to be amateurs, rather than sophisticated research personnel and even human studies have rarely used more than two raters of the same individual. Our findings provide support for claims that personality is dependent upon biological factors with a long evolutionary history, such as brain anatomy and chemistry. The reliability of assessments by the participants and their ability to utilise personality descriptors with another species also raises interesting questions regarding the legitimacy of everyday use of psychological terms to describe animal behaviour.