We present the clinical, biological, endocrinal and psychological characteristics of a 48,XXYY adult. The 43-year-old male examined is the first reported case of this XY polysomy concomitant with type 2 diabetes. Endocrine investigations suggested dysfunction of Leydig and Sertoli cells whereas the pituitary function appeared normal. We compare the phenotypic, behavioral and pathological features of the syndrome in our patient with other reports in the literature.