Abstract: AIM:To probe into the risk factors for acute coronary syndrome (ACS) in patients <35 years old. METHODS: ACS in patients aged 18-35 years old from January 2005 to August 2010 were selected as case group. Age- and gender-matched non-ACS patients treated at our hospital during the same period were selected as the control group. Clinical characteristics in the two groups were investigated and recorded, and single-factor analysis and multivariate analysis were performed to analyze the risk factors for ACS in patients <35 years old. RESULTS: There were 338 included cases in each group. Single-factor analysis indicated that the number of patients with smoking, concomitant essential hypertension, diabetes mellitus, dyslipidemia, increased BMI, and sleep deprivation in the ACS group was higher than in the non-ACS group, and the multivariate analysis indicated that the above-mentioned factors were independent risk factors for ACS in patients <35 years old, with OR values, respectively, 2.0, 2.3, 2.9, 2.4, 3.2 and 1.5. CONCLUSION: In addition to smoking, concomitant essential hypertension, diabetes mellitus, dyslipidemia, and increased BMI along with sleep deprivation are also independent risk factors for ACS in patients <35 years old.