Levels of lipoprotein (a) (Lp[a]) and various hemostatic factors were studied in 132 Japanese aged >75 years (mean 83). The group consisted of 50 healthy persons, 36 hypertensive subjects, 31 patients with chronic cerebral infarction, and 15 with coronary artery disease. Lp(a) levels were slightly lower in the healthy "old old" subjects than in the 184 healthy younger adults (mean ± SD: 10.7 ± 7.9 vs 12.1 ± 10.1 mg/dl). There were no gender-related differences in the Lp(a) levels of healthy adults and healthy old old subjects. Lp(a) levels were higher in the hypertensive old old subjects (14.6 ± 15.4 mg/dl) and the old old patients with cerebral infarction (21.3 ± 16.2 mg/dl) and coronary artery disease (26.5 ± 20.4 mg/dl). The prevalence of subjects with high Lp(a) levels (>30 mg/dl) was the greatest among old old patients with coronary artery disease (27%). Lp(a) levels in the 132 old old subjects showed positive correlations with sialic acid, fibrinogen, factor VII activity, and D-dimer levels. These results indicate a close association between Lp(a) levels and atherothrombotic disease as well as the characteristics of Lp(a) as an acute phase reactant in old old Japanese. Subjects with higher Lp(a) levels may develop cardiovascular disease later in life, whereas the remaining healthy old old subjects have lower Lp(a) levels.