Objectives: Little is known about patients without known modifiable risk factors presenting initially with acute coronary syndrome (ACS). This study assessed baseline characteristics and outcomes of ACS patients with and without the known modifiable risk factors arterial hypertension, dyslipidemia, obesity, smoking or diabetes. Methods: All ACS patients enrolled in the AMIS Plus Registry between 1997 and 2010 were analyzed until hospital discharge; a subgroup was re-assessed at the 1-year follow-up. Outcome measures were in-hospital mortality and major adverse cardiac or cerebrovascular events (MACCE) defined as a composite outcome of mortality, re-infarction and cerebrovascular events. Results: Of 33,306 patients, 2,125 (6.4%) had none of these modifiable risk factors. They were older (males), had less moderate or severe comorbidities and were more frequently in Killip class I on admission. Treatment of ACS patients with or without modifiable risk factors was similar with regard to interventional therapies and use of antiplatelet agents. In-hospital mortality was lower in patients without modifiable risk factors but in-hospital MACCE and 1-year survival was similar. Conclusion: Lack of modifiable risk factors was an independent predictor of lower in-hospital mortality but not of MACCE in patients who presented with ACS.