The plasma concentrations of homocysteine and lipoprotein A are independent risk factors for atherosclerotic vascular disease. Nitric oxide (NO) and folate values are also important in atherogenesis. The authors aimed to evaluate these parameters in patients having coronary artery bypass surgery (CABS) before 50 years of age and in their children. In 31 patients having CABS, 47 children of these patients, and 28 normal control subjects, homocysteine, NO, vitamin B 12, folate, lipoprotein A, triglyceride, total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, apolipoprotein A1, and apolipoprotein B values were determined. Homocysteine values of the patients with premature coronary heart diseases and their children were significantly higher than those of controls (p < 0.031 and p < 0.006, respectively). Also, NO levels were significantly higher in both groups than in controls (p < 0.001 and p < 0.031, respectively). B12 values were significantly higher in both groups (p < 0.05 and p < 0.033, respectively). Lipoprotein A levels were higher in both groups but not significantly so.