Objective: To screen for CLCN2 mutations in apparently sporadic cases of aldosterone-producing adenomas (APAs). Description: Recently, CLCN2, encoding for the voltage-gated chloride channel protein 2 (CIC-2), was identified to be mutated in familial hyperaldosteronism II (FH II). So far, somatic mutations in CLCN2 have not been reported in sporadic cases of APAs. We screened 80 apparently sporadic APAs for mutations in CLCN2. One somatic mutation was identified at p.Gly24Asp in CLCN2. The male patient had a small adenoma in size but high aldosterone levels preoperatively. Postoperatively, the patient had normal aldosterone levels and was clinically cured. Conclusion: In this study, we identified a CLCN2 mutation in a sporadic APA comprising about 1% of all APAs investigated. This mutation was complementary to mutations in other susceptibility genes for sporadic APAs and may thus be a driving mutation in APA formation.