and/or their metabolites. The main objective of the present study was to determine (n 20) plasma bioavailability and disposition in the liver, muscle, brown adipose tissue (BAT) and white adipose tissues (mesenteric and perirenal) in rats after a long-term consumption of three doses of grape seed phenolic extract (5, 25 and 50 mg/kg body weight) for 21 d in order to determine whether there is a dose–response relationship. Glucuronidated conjugates (total glucuronidated conjugates: C5 mg/kg 1·9; C25 mg/kg 6·4; C50 mg/kg 27·7mmol/l plasma) followed by methyl glucuronidated conjugates (total methyl glucuronidated conjugates: C5 mg/kg 1·98; C25 mg/kg 4·48; C50 mg/kg 12·5mmol/l plasma) were the main flavanol metabolites quantified in plasma, also detecting a dimer in its free form (C25 mg/kg 0·74; C50 mg/kg 0·79mmol/l plasma). Each of the studied organs has a particular behaviour of accumulation and response to the assayed grape seed extract doses, with an exponential bioavailability–dose relationship in BAT, in which flavanols could play an important role in the reduction or prevention of obesity, modulating the functionality of that tissue.