Sexual dysfunction is an important problem in diabetic patients. Frequency of dysfuncti¬on in diabetic men ranges from 27.5 to 75 % in various studies. Normal sexual function is dependent on harmonious integration of endocrine, neurologic and vascular systems. We evaluated sexual endocrine function in diabetic patients. Plasma follicle stimulating hormone (FSH), luteinizing (LH), prolactin (PRL), free testosterone (T), estradiol (E) levels were measured in dia¬betic male and female patients and healthy controls. In our study, 75 diabetic patients (53 female, 22 male) aged 22-78 years and 35 nondiabetic controls (25 female, 10 male) aged 20-57 years were investigated. Plasma hormone levels were determined by radioimmunoassay. In male diabetic group, mean plasma FSH, LH, T and PRL levels were 8, 72IU/L, 13, 36 pg/ml and 147, 51IU/L respectively. Mean hormone values of the male patients were not significantly different from the values of control group (p > 0.05). In premenopausal female diabetic group, mean plasma FSH, LH, E and PRL levels were 11, 04 IU/L, 7, 36 IU /L, 73, 52 pg/ml and 188, 73 IU /ml respectively. Mean plasma FSH value was significantly higher in pre¬menopausal diabetic female patients than the value of premenopausal controls (p < 0.01). Mean plasma LH, E, T and PRL values in premenopausal female diabetics and in postmenopausal female diabetics were not significantly different than the levels of their control groups (p > 0.05 andp > 0.05). Our results suggested that, sexual dysfunction in diabetic patients is not related to hormonal insuffici-'ency but may be the result of psychological, neurological and vascular involvement of disorder.