This article describes the epidemiology of injuries collected in the Injury Surveillance System in Leon Hospital in Nicaragua. A total of 6659 persons were treated for injuries in 2004. It was discovered that 88% of all injuries were unintentional, 9% involved interpersonal violence, 2% were self-inflicted and 0.2% was undetermined. Men accounted for 64.7% of the cases, with the highest rate among 20 - 24 year olds (5625.8 per 100,000 inhabitants). Among women, the highest rate was in those aged 64 years and older (5324.2 per 100 000 inhabitants). The most common mechanisms were falls (33.9%), blunt force (26.8%), cut/pierce/stab (15.1%) and transportation-related (12.8%). These results indicate the need to identify prevention strategies for those injuries that were most commonly treated in emergency, such as unintentional falls among older women, self-inflicted poisoning among young women and blunt force and transportation-related injuries among young men.