We describe below a case of Zellweger syndrome case with facial dysmorphism, profound hypotonia, and hepatomegaly. He died at the age of 2 months. Zellweger syndrome is a disease marked by the absence of hepatic and renal peroxisomes. Because peroxisomes have many vital anabolic and catabolic functions within the cell, their absence results in profound cellular dysfunction. A biochemical study of plasma revealed elevation of very long chains of fatty acids and pipecolic acid, consistent with peroxisomal disorder. The cultured skin fibroblasts showed a marked decrease in plasmalogen synthesis enzyme : dihydroxyacetonephosphate acyl transferase(DHAP-AT) The clinical characteristics and biochemical findings led to the diagnosis of Zellweger syndrome. The pattern of inheritance is autosomal recessive, hence genetic counseling can help the families. In infantile hypotonia patients with unknown cause, peroxisomal disorder should be included in the differential diagnosis. We report the first confirmed case of Zellweger syndrome by enzyme assay in Korea.