Nineteen males with a well-developed postconcussional syndrome were studied by CT-scan, by psychometric testing and by endocrinological evaluation including a variety of laboratory tests and an assessment of sexual function, 68% had cerebral atrophy on CT-scan and 79% were intellectually impaired, 37% to a severe degree. Sexual dysfunction (reduced libido and/or erective dysfunction) related to the head injury occurred in 58%, and severe intellectual impairment was significantly more frequent in this group. Increased plasma concentration of follicle stimulating hormone was observed in 37%, suggesting a reduced spermiogenesis. The possibility of a primary hypothalamic disorder causing reduced spermiogenesis is raised. Otherwise no radiological or laboratory evidence of major hypothalamic-pituitary dysfunction was demonstrated. The high frequency of cerebral atrophy and intellectual deterioration in postconcussional syndrome suggests organic brain dysfunction, but not causal relationship was established.