Marked variability in the treatment of patients with acute coronary syndrome has been observed in international and single-country studies for more than 15 years. This variability is associated with specific patient characteristics, such as being female or diabetic, but is also influenced by the center providing treatment and the physician in charge of care. It has repeatedly been demonstrated that, paradoxically, patients at a higher risk receive less complete treatment or are treated less in accordance with guidelines. Knowledge of all the factors that influence treatment variability combined with the implementation of measures to minimize them would help improve patient prognosis.