Primary hyperoxaluria type 1( PH1) is a rare autosomal recessive inherited disorder causing oxalate accumulation in multiple organs. Although some cases of PH1 were reported, PH1 has not adequately been surveyed in Korea. This study was conducted to determine the clinical characteristics, type of AGXT mutation, and outcome in children diagnosed with PH1 in Korea. We performed a retrospective cohort study of patients who diagnosed as PH1 from 2008 to 2016 at three tertiary care centers in Korea. The diagnosis was made upon the presence of mutations on AGXT gene and urinary biochemistry. We identified eight PH 1 patients. The median ages both at diagnosis and at the onset of initial symptoms were 2 (range : 0.2-10) years and 0.8 (range : 0.2-3) years, respectively. Initial serum creatinine level showed end-stage renal failure in six (75%) patients. Five (62.5%) patients received liver transplantation, among them three (60%) patients had both liver and kidney transplantation. The AGXT gene study revealed eight different mutations. A c.33dupC mutation was commonly detected in six patients, and there were four other truncating mutations (c.33delC, c.577dupC, c.681-1G＞A, c.331C＞T) and three missense mutations (c.335C＞A, c.568G＞A, c.346G＞C). We found that c.33dupC mutation is the dominant mutation type in Korea. Two patients who had a compound heterozygous mutation of one truncating mutation and one missense mutation showed a remarkably better clinical outcome than others.