PURPOSE: To evaluate the CT findings and clinical significance of left atrial wall calcification in patients who had undergone mitral valve replacement. MATERIALS AND METHODS: The unenhanced chest CT scans of 36 consecutive patients who had undergone mitral valve replacement were retrospectively reviewed, and left atrial calcification was found in 15. To determine the clinical significance of this, the CT findings were assessed in terms of the diameter of the left main pulmonary artery, the interval between previous surgery and scanning, and pulmonary arterial pressure. RESULTS: Left atrial wall calcification was either focal (linear, n=7; nodular, n=5), or diffuse (involving at least one-fourth of the left atrial wall) (n=3), and associated left atrial thrombus was found in two patients. Systolic pulmonary arterial pressure was significantly higher in those with calcification than those without (p<0.05), though between these groups there was no significant difference in the diameter of the left main pulmonary artery or the time interval between previous surgery and CT scanning. CONCLUSION: Left atrial wall calcification is a common finding in patients who have undergone mitral valve replacement, particularly in those with high pulmonary arterial pressure.