Patterning of proteins is critical to protein biochips. Printing of layers of proteins is well established, as is adsorption of proteins to surfaces properly modified with surface chemical functionalities. The authors show that simple methods based on soft lithography stamps can be used to prepare functional antibody chips through both these routes. Both methods incorporate transfer of the stamp material poly(dimethylsiloxane) (PDMS) to the biochip, whether intended or not intended. The results indicate that microcontact printing of proteins always includes PDMS transfer, thereby creating a possibility of unspecific adsorption to a hydrophobic domain. © 2008 American Vacuum Society.