A nanodrum of an unsupported L-alpha-phosphatidylcholine bilayer on a similar to 7 mu m pore was studied using a new experimental setup that permits atomic force microscopy (AFM) in conjunction with the electrical determination of trans-bilayer channels, thus checking its unilamellar character. In these nanodrums, the bilayer engulfs the intruding AFM tip with an adhesion similar to the attraction between two mica supported bilayers brought into close contact. Using this response and the finding of a nonlinear, behiivior of the Canham-Helfrich elastic model allows for the simultaneous determination of the elastic proper-ties of the membrane. A- bending modulus (k = 1.5 +/- 0.6 x 10(-19) J) and a lateral tension (sigma = 1.9 +/- 0.7 mN/m) were determined for this case Most importantly, an adhesion constant (w = 4.6 +/- 2.2 mJ/m(2)) was determined from a particular response to deformation of large membrane patches.