In a 26-year-old male with 17 alpha-hydroxylase deficiency, endocrinological examinations were performed not only after, but also before the onset of clinical signs and symptoms. In addition, the pathophysiological role of the renal kallikrein-kinin system was investigated in this patient. In spite of the fact that this disease is congenital, in the mechanism of its onset, this patient had a period of endocrinological normality before onset; that is, 9 months before onset, both ACTH and cortisol were within the normal range, although the former would be significantly higher and the latter significantly lower than normal values after the onset. In this case, both urinary kallikrein and kininase excretions abnormally increased and then returned to normal after dexamethasone treatment.