BACKGROUND: Adrenoleukodystrophy refers to an inherited disorder that mainly affects the adrenal gland, and the nervous system. The most common type is X-linked adrenoleukodystrophy (XALD). The main presenting symptoms are behavioral changes. However, endocrinological manifestations are also important and need to be clarified especially adrenal insufficiency which is a lifethreatening condition that can be prevented. OBJECTIVE: To review the endocrinological and the adrenal functions in X-linked ALD. SUBJECTS AND METHOD: The medical records of four patients diagnosed with ALD at the Endocrinology and Metabolic Unit, Department of Pediatrics, King Chulalongkorn Memorial Hospital between 1998 and 2000 were reviewed. The diagnoses were confirmed by elevated very long chain fatty acid (VLCFA) levels and the typical changes seen on magnetic resonance imaging (MRI) of the brain. The adrenal functions in these patients were studied. RESULTS: All patients presented between 7-11 years of age with learning problems and behavioral changes, without symptoms of adrenal insufficiency such as nausea, vomiting and abdominal pain. However, the physical signs of adrenal insufficiency such as generalized hyperpigmentation particularly on the nipples, skin creases and genitalia were present. The laboratory investigations revealed normal blood sugar and serum electrolytes. The adrenal functions were revealed as follows. Basal ACTH levels were high in 2 cases (290, > 1,250 pg/mL). Basal cortisol level was low in 1 case. ACTH stimulation tests revealed subnormal responses in 3 cases. Magnetic Resonance Imaging of the brain showed white matter degeneration in the occipital area in 2 cases and frontal area in 2 cases. CONCLUSION: Adrenal insufficiency can be detected by laboratory evaluation despite the lack of symptoms, therefore, the adrenal function should be evaluated in X-ALD at diagnosis for proper management.