For a number of rare adrenal disorders, some of which are life threatening in childhood, laboratories need access to specialist endocrine investigations. Measurements of hormones in blood samples may be diagnostic in some cases but not all of the requisite steroid hormone assays are available. Multiple plasma steroid measurements may be required to prove the nature of a steroid biosynthetic disorder but in newborn children immunoassays, performed without prior solvent extraction, can be misleading. A urine steroid profile by gas chromatography coupled with mass spectrometry examines many steroid metabolites simultaneously and provides specific diagnostic information. A urine steroid profile can provide precise information of the secretory nature of tumours and causes of virilization, salt loss and hypertension often from a spot urine sample rather than a 24 h collection. However, a steroid profile is not helpful in making a diagnosis in neonatal genetic males with poorly developed genitalia.