To study the influence of cutaneous blood flow upon the transdermal penetration of drugs, an original in vivo model, the bipediculated dorsal flap (BDF) of the hairless rat is described. This model is constituted by a dorsal cutaneous muff on both sides of the spinal column. The blood circulation was maintained symmetrically on both skin insertion pedicles. Two radiotracers, 86Rb and 201T1 (respective half-lives: 18 and 3 days), known to measure nutritional blood flows, are compared in this model. In the back skin, over and under the flap, mean blood flow (expressed as percentage of injected dose per gram skin) was similar with Rb (9.5 ± 3.1) ·10-2 and Tl (10.2 ± 2.1)· 10-2. Equivalent values were obtained in BDF skin (non ligated pedicle): Rb (8.4 ± 1.3) · 10-2, Tl (9.5 ± 2.7) · 10-2. In BDF skin, cutaneous blood flow was lower by 70–91 % in the ligated pedicle (compared to the nonligated) for both radioisotopes. Identical 86Rb and 201T1 distributions suggest the use of 201T1 for further experiments of cutaneous b