We diagnosed a unique peroxisomal disorder in a 32-year-old man with profound mental retardation, mild facial dysmorphism, retinal pigmentary degeneration, seizures, and sensorineural deafness. Although plasma very-long-chain fatty acid profile suggested X-linked adrenoleukodystrophy, marked reduction in fibroblast lignoceric acid oxidation and the presence of cytosolic catalase were consistent with Zellweger syndrome (ZS). Unlike ZS, functional peroxisomes were present as indicated by the density of peroxisomes (1.175 gm/ml) similar to peroxisomes from control cells and by partial deficiencies of fibroblast phytanic acid oxidation and dihydroxyacetone phosphate acyltransferase activity. These findings indicate that this patient has a previously undescribed group 3 peroxisomal disorder (multiple peroxisomal enzyme deficiencies with preserved peroxisomes).