Background: Peroxisomes are organelles responsible mainly for metabolism of lipids and peroxides. Lack of peroxisomes or dysfunction in any of their normal functions is the cellular basis for human peroxisomal disorders (PDs).     Aim of the Work: diagnosis of peroxisomal disorders among a high risk group of Egyptian patients using gas chromatography mass spectrometry. Subjects and Methods: Forty six patients suspected to have peroxisomal disorders were included in this study. Their ages ranged from 2 to 20 years. They were referred to The Biochemical Genetics Department, National Research Centre from all over Egypt. Forty one (89%) were males while five were females (11%). Parental consanguinity was positive in 28 cases (61% out of 46). Very long chain fatty acids were quantified after extraction from plasma of all cases using gas chromatography/mass spectrometry (GC/MS) technique. Results: The present study included 46 cases suspected clinically to have one of the peroxisomal disorders; four of them (8.7%) proved to have X-linked adrenoleukodystrophy by quantitative determination of the very long chain fatty acids after extraction from their plasma. The other 42 cases showed normal profile for very long chain fatty acids. Conclusion:    This study showed that GC/MS analysis for VLCFA discriminates patients from controls, representing a non-invasive, reliable, specific and sensitive method for the diagnosis of peroxisomal disorders.