The objective of this study was to demonstrate the presence of leptospires in equine urine, as evidence for a potential role of horses in transmission of this organism. Thoroughbred horses (aged 2–5 years, n=276) from Rio de Janeiro, Brazil, were studied. After a severe storm, the premises of the animals remained flooded for 72 h. Blood samples for serology were collected on days 20 and 35 (day of storm=day 0). On day 20, 132 (47. 8%) horses were seroreactive (titre o200) and, of these, 23 (31. 0%) had increased antibody titres on day 35. Furthermore, 34 urine samples (for PCR and culture) were collected from seroreactive horses on day 35. Copenhageni was the most frequent serovar (88. 8% of reactive titres). Although none of the urine samples were culture positive, 12 (35. 2%) were PCR positive. This is apparently the first report of evidence of leptospires in urban horses. Furthermore, we suggest that these animals can play a role in the transmission of leptospirosis in urban areas.