Background: The objective was to analyze the incidence, risk factors, management, and complications of acute myocardial infarction (AMI) in the young patient in Spain. Methods: Clinical characteristics, treatment, and outcome were analyzed in patients younger than 45 years admitted with an AMI diagnosis to the Coronary Units of 58 Spanish hospitals from 15th May to 15th December 2000. Results: Six thousand two hundred and ten consecutive patients were registered, 7% out of them were <45 years old. Outcome was better in the younger group, with a lower mortality rate at 28 days (3.7 vs. 11.9%; p < 0.001), demonstrating that age <45 years is an independent protective factor for mortality (relative risk: 0.41; 95% CI: 0.23–0.73; p < 0.001). This difference remained at 1-year follow-up. Conclusions: AMI in young patients presents distinct clinical characteristics, a different treatment, management and outcome with respect to the older group.