Aging is associated both with clinically important hormonal changes and with a decrease of energy expenditure. Leptin is a protein hormone, predominantly produced by adipocytes, which is presumed to be involved in the regulation of appetite and energy expenditure. The present study aimed to assess the relationship between leptinaemia and age. 144 healthy subjects (72 females and 72 males) age from 20 to 93 years were enrolled in this study. All studied subjects were divided according to the age into five groups (group A comprised subjects aged 20 to 40 years, group B--from 41 to 60 years, group C--from 61 to 70 years, group D--from 71 to 80 years and group E--aged over 81 years). In all examined subjects plasma leptin, insulin and glucose concentrations were estimated at 8 a.m., 4 p.m. and 12 p.m. respectively. Body mass index (BMI) was also calculated in all studied subjects. Basal (8 a.m.) plasma leptin concentration did not differ significantly in all age groups: A = 10.4 +/- 1.33; B = 12.5 +/- 2.18; C = 9.8 +/- 1.48; D = 14.4 +/- 3.12; E--10.5 +/- 1.99 ng/ml). In all examined groups plasma leptin concentrations were significantly higher at 12 p.m. than at 8 a.m. and 4 p.m. respectively. Females were characterized by significantly higher plasma leptin concentration in all age groups. A significant positive correlation was found between plasma leptin concentration and BMI in all age groups (except group A). No relationship between age and plasma leptin concentration were found, as analyzed both by correlation and multivariate regression analysis, respectively. From results obtained in this study we may conclude that age does not influence significantly leptinaemia.