MOTIVATION AND METHOD: Small-molecule inhibitors targeting the adenosine triphosphate (ATP) binding pocket of the catalytic domain of protein kinases have potential to become drugs devoid of (major) side effects, particularly if they bind selectively. Here, the sequences of the 518 human kinases are first mapped onto the structural alignment of 116 kinases of known three-dimensional structure. The multiple structure alignment is then used to encode the known strategies for developing selective inhibitors into a fingerprint. Finally, a network analysis is used to partition the kinases into clusters according to similarity of their fingerprints, i.e. physico-chemical characteristics of the residues responsible for selective binding.