A urinary steroid excretion pattern of a 3-wk-old newborn, suffering from 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) deficiency, has been produced, employing capillary gas chromatography and subsequent mass spectrometric identification of the various excreted steroids. The diagnosis could be established, apart from the clinical symptoms, on the basis of a grossly elevated excretion of 16-OH-DHEA and 16-OH-pregnenolone, combined with mass spectrometric identification of the following steroids: 17-OH-preganolone, pregnanetriol, pregnanolone, pregnenetriol and 17-OH-pregnenolone.