Hyperhomocysteinemia is currently regarded as an independent and modifiable risk factor for ischemic vascular diseases and thrombosis. We measured fasting plasma total homocysteine levels by HPLC with fluorescence detection in 30 patients presenting with acute coronary syndromes and 30 age and sex-matched control subjects. Demographic data, classical risk factors (systolic blood pressure, diabetes mellitus, smoking, ethanol intake, family history of ischaemic heart disease) and life-style habits were recorded. Lipid fractions including total cholesterol, triglycerides, HDL-cholesterol, total cholesterol/ HDL-cholesterol ratio, serum creatinine, LDL-cholesterol and vitamins involved in the metabolism of homocysteine, folic acid and vitamin B12 were also assessed. Total fasting homocysteine concentrations were significantly higher in the patient group (12.2 +/- 1.01 mu mol/l) than in the control subjects (7.05 +/- 0.36 mu mol/l; p < 0.0001). Homocysteine correlated positively with age (r = 0.617; p < 0.01) and serum creatinine (r = 0.457; P < 0.01) in the patient group. Hyperhomocysteinemia was not associated with vitamin B12 or folate deficiency states. Vitamin B12 concentration was 273 +/- 16.4 ng/l in the control group and 284.3 +/- 32.2 ng/l in the patient group (P = NS). Serum folate concentration also was not significantly different between controls and patients; 7.57 +/- 0.58 mu g/l and 8.05 +/- 0.72 mu g/l, respectively. Since no significant difference was observed in the lipid parameters between patients and controls, the hyperhomocysteinemia in the patient group supports the view that homocysteine is an independent risk factor for cardiovascular diseases. Our results strongly suggest that elevated homocysteine levels are among the interacting factors in the complex, multifactorial pathophysiology of ischemic heart disease.