The prevalence and extent of immunoglobulin G4 (IgG4)-positive cell infiltration were investigated in 282 surgical samples of aortic wall and aortic valve. Tissue infiltration of IgG4-positive cells was observed in 24 (17.3%) of 139 aortic valve samples and 46 (32%) of 143 aortic wall samples, and the condition of IgG4-positive cell infiltration > 30/hpf together with IgG4/CD138 ratio > 40% was observed in 2 (1.4%) of aortic valve samples and 14 (9.8%) of aortic wall samples. Among 275 patients, preoperative serum IgG4 level was available in 48 patients (50 samples), and it was > 135 mg/dL in only one patient. Of these 48 patients with serum IgG4 measurement, 29 patients had aortic valve stenosis and 12 had aortic aneurysm. Compared with 23 aortic stenosis patients without tissue infiltration of IgG4-positive cells in the aortic valve, six patients with IgG4-positive cell infiltration had a more prevalent smoking history (26% versus 83%) and borderline significantly higher serum IgG4 (median, 24.5 mg/dL versus 55.5 mg/dL), although either preoperative peak pressure gradient between left ventriculum and aorta or aortic valve area did not differ significantly between groups. Compared with six aortic aneurysm patients without tissue infiltration of IgG4-positive cells in the aortic wall, six patients with IgG4-positive cell infiltration had borderline significantly higher serum IgG4 (median, 28.9 mg/dL versus 68.2 mg/dL). The current study showed that tissue IgG4-positive infiltration is not a rare occurrence in the aortic stenosis and aortic aneurysm. Clinical significance of tissue IgG4-postive cell infiltration in these patients requires further investigation.