Abstract BACKGROUND: Increased levels of lipoprotein (Lp)(a) is a risk factor for coronary heart disease. In this study we evaluated levels of Lp(a) in patient with acute myocardial infarction (AMI) aged less than 50 years old in comparison to controls. METHODS: In this case-control study, we compared 98 patients with AMI (case group) and an equal number of age- and sex-matched healthy subjects (control group). Serum Lp(a) level was measured after 12 hours of fasting in both groups. RESULTS: The mean age of the case and control groups was not significantly different (45.28 ± 5.09 vs. 44.89 ± 5.22 years, respectively P = 0.52).The mean Lp(a) level was significantly higher in the case group than in the control group (32.5 ± 24.5 vs.25.2 ± 22.6 mg/dl, respectively P = 0.04). Prevalence of LP(a) ≥ 30 mg/l was significantly higher in case group than in control group (43.5% vs. 27. %, respectively, P = 0.016, OR = 3.22, 95% CI = 1.24-8.3). CONCLUSION: Because of high prevalence of high LP(a) in premature AMI, it is necessary to control this disorder in young adults for preventing delayed MI.[R1] Keywords: Highlipoprotein (LP)(a), Premature myocardial infarction, Case- control study [R1]The sentence does not make sense.