Background: The relationship between coronary artery disease (CAD) and dyslipidemia in acute coronary syndromes has been rarely demonstrated in clinical and epidemiological studies., Objective: To evaluate the association between lipid profile and severity of CAD in patients with acute coronary syndrome without ST-segment elevation., Methods: In this retrospective study, the authors reviewed medical records of 107 consecutive patients diagnosed with acute coronary syndrome (ACS) without ST-segment elevation admitted within a one-year period and who had undergone coronary angiography during hospitalization. Laboratory evaluation included serum levels of lipid fractions. Severity of CAD was determined by evaluating the number, degree, and score of coronary artery obstructions. For statistical analysis, the Students t test, chi-square test and ANOVA with statistical significance set at p<0.05, as well as multivariate analysis were performed., Results: A total of 107 patients were included; 94(88%) had CAD, of which 50 (53.2%) were males with predominance of multivessel disease. As regards the lipid profile, 64(59.8%) patients were observed to have TC<200mg/dl, 33(30.8%) had HDL<40 mg/dl, and 38(35.5%) had LDL<100mg/dl. The analysis of coronary angiographies showed that 94(88%) patients had CAD, and 84% had > 70% stenosis. In the association between lipid profile and CAD, we observed a higher TC/HDL ratio in the multivessel and two-vessel groups in comparison with the one-vessel group (4.3+/-2, 4.0+/-1.7, 2.9+/-1.6, respectively) with ANOVA p=0.049. In the multivariate analysis, the TC/HDL ratio remained a significant predictor (p = 0.016)., Conclusion: The TC/HDL ratio was a marker of severity of CAD in relation to the number of vessels affected, thus demonstrating that the lipid profile can be a determinant of severity in patients with ACS without ST-segment elevation.