Background. Primary aldosteronism (PA) is a type of secondary hypertension with prominent left ventricular hypertrophy (LVH). Unilateral aldosterone-producing adenoma (APA) is the most common subtype that can be cured by adrenalectomy. Objective. To investigate left ventricular structural change after surgery and the factors associated with the degree of LVH regression in patients with PA. Methods. We performed a retrospective analysis in the Taiwan Primary Aldosteronism Investigation (TAIPAI) database, including demography, biochemical data, echocardiography and medication. Results. From July 1994 to January 2007, 20 patients (8 men) with APA receiving adrenalectomy and having pre- and postoperative echocardiography were selected. After 21 ± 19 months post operation, the left ventricular wall thickness and left ventricular mass index (LVMI) decreased significantly. The decrease of LVMI is significant only in patients who had LVH before operation. In analysis of factors associated with net LVMI decrease (ΔLVMI; post-operative LVMI - pre-operative LVMI), only pre-operative LVMI ( r = -.783, p < .001), and ΔSBP ( r = .472, p = .036) significantly correlated with ΔLVMI. In conclusion, LVH in PA could be significantly reversed by adrenalectomy. Pre-operative LVMI and ΔSBP were associated with the degree of LVMI decrease. Conclusion. LVH in PA could be significantly reversed by adrenalectomy. Pre-operative LVMI and ΔSBP were associated with the degree of LVMI decrease.